A content data storage device which stores content data which includes a wide-band content and a narrow-band content includes a buffer memory temporarily storing the content data to be externally input, a storage unit including a plurality of nonvolatile memories configured to be written for each page and storing in turn the content data to be output from the buffer memory, and a controller controlling an output from the buffer memory so as to output content data of one page to the storage unit when the content data of not less than one page is stored in the buffer memory, wherein the controller adds dummy data to the narrow-band content as the content data of one page, if the narrow-band content stored in the buffer memory reaches the prescribed capacity.