diff --git a/Coffeefy/AppDelegate.swift b/Coffeefy/AppDelegate.swift
index 7595043..7f80382 100644
--- a/Coffeefy/AppDelegate.swift
+++ b/Coffeefy/AppDelegate.swift
@@ -11,8 +11,10 @@ import MASPreferences
 import ReachabilitySwift
 import CoreWLAN
 import Alamofire
+import CocoaLumberjack
 
 public let PostResultNotification = NSNotification.Name("PostResultNotification")
+public let ddLogLevel: DDLogLevel = DDLogLevel.info
 
 let keyIgnoreVersion = "Ignore Version"
 
@@ -40,6 +42,17 @@ class AppDelegate: NSObject, NSApplicationDelegate {
     let bot = LoginBot()
 
     func applicationDidFinishLaunching(_ aNotification: Notification) {
+        // initiate logger
+        #if DEBUG
+            DDLog.add(DDTTYLogger.sharedInstance())
+        #else
+            let fileLogger = DDFileLogger()
+            fileLogger?.rollingFrequency = 7 * 60 * 60 * 24 // a week
+            fileLogger?.logFileManager.maximumNumberOfLogFiles = 1
+            DDLog.add(fileLogger)
+        #endif
+        
+        // status menu
         statusItem.menu = statusMenu
         loadStatusImage(name: "coffeefy3")
         
@@ -53,7 +66,7 @@ class AppDelegate: NSObject, NSApplicationDelegate {
         do {
             try reachability.startNotifier()
         } catch {
-            NSLog("Could not start reachability notifier")
+            DDLogWarn("Could not start reachability notifier")
         }
     }
 
@@ -67,12 +80,12 @@ class AppDelegate: NSObject, NSApplicationDelegate {
         }
         
         // 스타벅스 SSID일 때만 반응
-        let ssid = CWWiFiClient()?.interface(withName: nil)?.ssid() ?? ""
+        let ssid = CWWiFiClient()?.interface(withName: nil)?.ssid() ?? "[Empty SSID]"
         if ssid.lowercased().contains("starbucks") {
             startAnimatingStatusImage()
             bot.login()
         } else {
-            NSLog("This application works only with Starbucks Wifi network")
+            DDLogWarn("Unknown SSID - \(ssid) is not Starbucks Wifi network")
         }
     }
     
diff --git a/Coffeefy/LoginBot.swift b/Coffeefy/LoginBot.swift
index 4c75756..554ed2e 100644
--- a/Coffeefy/LoginBot.swift
+++ b/Coffeefy/LoginBot.swift
@@ -9,6 +9,7 @@
 import Cocoa
 import WebKit
 import Alamofire
+import CocoaLumberjack
 
 let messageHandlerKey = "coffeefy"
 let firstURL = "http://first.wifi.olleh.com/starbucks/index_en_new.html"
@@ -26,6 +27,7 @@ class LoginBot: NSObject, WKScriptMessageHandler, WKNavigationDelegate {
         self.initWebview(wv)
         return wv
     }()
+
     var branch = ""
 
     func initWebview(_ webView: WKWebView) {
@@ -47,6 +49,7 @@ class LoginBot: NSObject, WKScriptMessageHandler, WKNavigationDelegate {
         Alamofire.request(firstURL).responseString { response in
             if let content = response.result.value {
                 if !content.hasPrefix("<script") {
+                    DDLogInfo("Moving to Google...")
                     // 다른 사이트로 먼저 이동해야 접속이 이루어짐 HTTP 프로토콜 필수
                     self.webview.load( URLRequest(url: URL(string: "http://google.com")!) )
                     // self.webview.load( URLRequest(url: URL(string: firstURL)!) ) // 에러가 발생하는 사례
@@ -55,7 +58,7 @@ class LoginBot: NSObject, WKScriptMessageHandler, WKNavigationDelegate {
                 }
             }
 
-            NSLog("This application works only with Startbucks Wifi network.")
+            DDLogWarn("This application works only with Startbucks Wifi network.")
             self.postResult(success: false)
         }
     }
@@ -67,8 +70,8 @@ class LoginBot: NSObject, WKScriptMessageHandler, WKNavigationDelegate {
             let content = try String(contentsOfFile: path!, encoding: .utf8)
             return content
         } catch let error {
-            NSLog("Error loading contentsOf url \(path)")
-            NSLog(error.localizedDescription)
+            DDLogError("Error loading contentsOf url \(path)")
+            DDLogError(error.localizedDescription)
         }
         
         return ""
@@ -97,11 +100,15 @@ class LoginBot: NSObject, WKScriptMessageHandler, WKNavigationDelegate {
             let name = UserDefaults.standard.string(forKey: "name") ?? ""
             let email = UserDefaults.standard.string(forKey: "email") ?? ""
             let phone = UserDefaults.standard.string(forKey: "phone") ?? ""
+
             webview.evaluateJavaScript("coffeefy({name:'\(name)', email:'\(email)', phone: '\(phone)', branch: '\(self.branch)'})", completionHandler: nil)
+            DDLogInfo("Trying to sign in... (name=\(name), email=\(email))")
         } else if body.hasPrefix("alert:") {
             let errorMessage = body.substring(from: body.characters.index(body.characters.startIndex, offsetBy: 6))
             notify(title: "인증 에러", subtitle: errorMessage, informativeText: nil)
             postResult(success: false)
+            
+            DDLogError("Authorization failed: \(errorMessage)")
         }
     }
     
@@ -114,6 +121,7 @@ class LoginBot: NSObject, WKScriptMessageHandler, WKNavigationDelegate {
         if host == "www.istarbucks.co.kr" || host.hasPrefix("www.google.") {
             webView.stopLoading()
             notify(title: "접속 성공", subtitle: "이제 스타벅스 와이파이를 사용할 수 있습니다.", informativeText: nil)
+            DDLogInfo("Successfully connected!")
             postResult(success: true)
         }
     }
diff --git a/Podfile b/Podfile
index 9c94912..684edff 100644
--- a/Podfile
+++ b/Podfile
@@ -5,4 +5,5 @@ target 'Coffeefy' do
 	pod 'MASPreferences'
     pod 'ReachabilitySwift'
     pod 'Alamofire', '~> 4.0'
+    pod 'CocoaLumberjack/Swift'
 end