A digital camera includes a CCD imager which outputs 640 pixels×480 lines of camera signal in a raster scan scheme. The camera signal outputted from the CCD imager is subjected to a predetermined signal processing whereby created are 640 pixels×480 lines of original image data and 80 pixels×60 lines of thumbnail image data. Both the created original image data and thumbnail image data are written to a SDRAM. The writing of the thumbnail image data is performed during a horizontal blanking period of the original image data. As a result, image data writing operation completes within a 1-frame period of time.