Pixel values of focus detection pixels are suitably corrected according to reducing occurrence of a residual error of correction. A digital camera ii includes a CCD, an AF detection circuit, a specific pixel correction unit and the like. The CCD has standard pixels and phase difference pixels arranged in a predetermined pattern on an imaging surface, and outputs an image signal of one frame. The AF detection circuit evaluates an in-focus state by referring to a pixel value of the phase difference pixels from the image signal. The specific pixel correction unit determines a first correction value by multiplying the pixel value of the phase difference pixels by a predetermined gain, and compares the first correction value with the pixel value of the standard pixels around the phase difference pixels. If the first correction value is equal to or less than the maximum of those pixel values and equal to or more than their minimum, the pixel values of the phase difference pixels are replaced with the first correction value. Otherwise, the pixel values of the phase difference pixels are replaced with a second correction value obtained by averaging the pixel values of peripheral pixels.