1. An image processing device for adjusting color balance in an image to be processed, comprising: a specific color pixel ratio calculation module configured to calculate a ratio of specific color pixels having a color within a first predetermined range in the vicinity of a specific chromatic color, from among all of the pixels present in an image to be processed; a specific color pixel average calculation module configured to calculate an average value of pixel values for the specific color pixels; a color balance correction value calculation module having a first computation mode for calculating a color balance correction value based on the specific color pixel ratio and the average pixel value for the specific color pixels; and a color balance adjustment execution module configured to execute the color balance adjustment for the entirety of the image to be processed, using the color balance correction value.