1. An image processing apparatus for processing a plurality of image data obtained by picking up images of an object in different photographing conditions, the image processing apparatus comprising: at least one processor functioning as: an obtaining unit configured to obtain the plurality of image data; a combining unit configured to combine the plurality of image data and generate combined image data; a first determination unit configured to execute first determination processing for detecting the object on at least one of the plurality of image data; and a second determination unit configured to execute second determination processing for specifying the object detected by the first determination unit on the combined image data, wherein the first determination processing is face detection processing for detecting a face from image data, and the second determination processing is at least one of face recognition processing for identifying which is the face detected in the first determination processing, and facial expression determination processing for determining a facial expression of the face detected in the first determination processing.