A content delivery system, a method thereof, and a content reproducing device are provided. The content reproducing device comprises a content separator, an insufficient content storing section, and a server. The content separator separates or divides content into an insufficient content and a complementary content. The insufficient content storing section stores the insufficient content sent (outputted) from the content separator. The server includes a storing means for storing the complementary content sent from the content separator, and sends the complementary content to the content reproducing device via a network. The content reproducing device acquires the complementary content from the server and the insufficient content from the insufficient content storing section. Thereafter, the content reproducing device reproduces the content using the insufficient content and the complementary content. Thereby, it is possible to provide a system and a method which save the trouble of checkin and/or checkout operation and thus enhance user's usability. Further, according to the system and the method, a content provider can charge a user for content each time a user reproduces content.