1. An image pick-up apparatus which includes an image pick-up device having a plurality of main pixels having high sensitivity and a large light receiving area and a plurality of sub-pixels having low sensitivity and a small light receiving area, comprising: storage means for storing control values for white balance adjustment which are set in association with each of said plurality of pixels; and white balance adjusting means for separately performing white balance adjustment of each of the image signals acquired from the plurality of pixels of said image pick-up device with using said corresponding control values, wherein said storage means stores a control value for white balance adjustment associated with said main pixel, and said white balance adjusting means performs white balance adjustment of an image signal from said main pixel with using said control value stored in said storage means and performs white balance adjustment of an image signal from said sub-pixel with using said control value and a color difference ratio of the image signals between said main pixel and said sub-pixel.