An image processing apparatus has a memory which stores a program and a processor which executes the program stored in the memory to acquire a plurality of picked-up images picked up by a plurality of image pickup systems, calculate a white balance of each of the plurality of acquired picked-up images, set a white balance of a joint of the plurality of picked-up images, individually calculate interpolated values between the calculated white balances and the set white balance of the joint by an interpolation function, individually and continuously vary the white balances in the plurality of picked-up images based on the calculated interpolated values to correct the white balances, individually adjust the plurality of picked-up images based on the calculated white balance of each of the plurality of picked-up images, the white balance of the joint, and the corrected white balances, and synthesize the plurality of adjusted picked-up images to generate a wide angle image.