An image processing apparatus that generates a three-dimensional image as a subtraction image from a first medical image and a second medical image which are three-dimensional images obtained by imaging a subject, the image processing apparatus includes an acquisition unit configured to acquire the first medical image and the second medical image, a determination unit configured to determine a resolution of the subtraction image, and, a subtraction image generation unit configured to generate the subtraction image having the resolution determined by the determination unit, wherein the determination unit determines a resolution of at least one axial direction among three axial directions configuring the resolution of the subtraction image, based on a resolution of the first medical image and a predetermined first resolution.