A digital camera (10) includes a CCD imager (16). An image signal corresponding to an optical image is output from the CCD imager (16), and an incident light amount to the CCD imager (16) is restricted by an aperture unit (14). A CPU (40) adjusts an exposure time period of the CCD imager (16) on the basis of an average luminance value of a normal evaluation area assigned to the center of a screen out of the image signals output form the CCD imager (16). The CPU (40) also adjusts an aperture amount of the aperture unit (14) on the basis of an average luminance value of a specific evaluation area assigned to the end of the screen out of the image signals output form the CCD imager (16).