An object of this invention is to quickly complete white balance calculation in photographing. To achieve this object, an image sensing apparatus includes an image sensing element in which a line on which first and second color filters are arranged and a line on which first and third color filters are arranged are alternately arrayed on pixels, an image sensing controller which forms an image of one frame by n fields (n is an odd number), and reads out pixel data of the image sensing element so as to contain all color components in each 1-field period, a white balance calculation device which performs process on the basis of image data read out from the image sensing element by the image sensing controller, and starts the process before read of one frame from the image sensing element is completed by the image sensing controller.