1. An image processing apparatus comprising: a generation unit configured to generate a subtraction image between a plurality of fundus images of an eye corresponding to a plurality of three-dimensional tomographic images obtained by capturing images of the eye at different times using a tomographic imaging unit, the tomographic imaging unit being configured to obtain the plurality of three-dimensional tomographic images using combining light obtained by combining returning light from the eye illuminated with measurement light and reference light corresponding to the measurement light; a display control unit configured to control a display unit to display the subtraction image and to display a marker indicating a position of at least one of a plurality of two-dimensional tomographic images in a state of being superimposed on the subtraction image; and a specifying unit configured to specify, by a position of the marker being specified on the displayed subtraction image, at least one of the plurality of two-dimensional tomographic images in at least one of the plurality of three-dimensional tomographic images, wherein the display control unit is configured to control the display unit to display the specified at least one of the plurality of two-dimensional tomographic images.