diff --git a/src/main/java/com/logpresso/scanner/Configuration.java b/src/main/java/com/logpresso/scanner/Configuration.java
index 047ee04..326398f 100644
--- a/src/main/java/com/logpresso/scanner/Configuration.java
+++ b/src/main/java/com/logpresso/scanner/Configuration.java
@@ -381,6 +381,13 @@ else if (!reportFile.isDirectory())
 			}
 		}
 
+		// exclude iCloud and Dropbox by default
+		String osName = System.getProperty("os.name");
+		if (osName != null && osName.toLowerCase().startsWith("mac")) {
+			c.excludePatterns.add("/Dropbox");
+			c.excludePatterns.add("/Library/Mobile Documents");
+		}
+
 		// check conflict between --report-csv and --report-json
 		if (c.reportCsv && c.reportJson && c.reportPath != null)
 			throw new IllegalArgumentException(