To provide an image data writing method whereby a user can intentionally select switching of a plurality of recording media without causing temporal discontinuity to moving picture data.

When the recording of the first half of the moving picture data to a first recording medium is started as an image file DSCF 1001A. AVI and the residual capacity of the first recording medium reaches less than 1MB, a message for urging the switching to a second recording medium is displayed on a liquid crystal panel and a buzzer sounds. When the residual capacity of the first recording medium reaches 0 MB, the write destination is switched, the recording of the latter half of the moving picture image data to the second recording medium is started as an image file DSCF 1001B. AVI, and a timer is started. When a write instruction button is depressed, the writing is continued. When a write rejection button is depressed, the write to the second recording medium is stopped and the image file DSCF 1001B. AVI is deleted. When the second recording medium is replaced and the write instruction button is depressed, the latter half of the moving picture data is written in the new second recording medium. After a lapse of 30 seconds without any instruction, the write to the second recording medium is continued.