1. An image processing apparatus comprising: a first tomographic image acquisition unit configured to acquire a first tomographic image of a subject's eye captured at a first time point that is a past time point; a first image capturing region acquisition unit configured to acquire a first image capturing region that is an image capturing region of the first tomographic image; a second tomographic image acquisition unit configured to acquire a second tomographic image of the subject's eye captured at a second time point later than the first time point; a second image capturing region acquisition unit configured to acquire a second image capturing region that is an image capturing region of the second tomographic image; and a display control unit configured to, if one image capturing region of the first image capturing region and the second image capturing region is larger than an other image capturing region that is different from the one image capturing region, perform control to provide, on a display portion, a display of both a tomographic image of only a partial region of the one image capturing region which is a corresponding region corresponding to the other image capturing region and a tomographic image of the other image capturing region.