When reliability of a defocus amount which is calculated using a signal from a region 50A is low, a digital camera expands the phase difference detection target region to the regions 50A, 50B, and 50C. Further, the digital camera calculates a defocus amount using a correlation operation result of an output signal group of pixel cells 31R in an odd numbered column and an output signal group of the pixel cells 31L in an odd numbered column and a correlation operation result of an output signal group of pixel cells 31R in an even numbered column and an output signal group of the pixel cells 31L in an even numbered column, in the regions 50A, 50B, and 50C.