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: 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; and a control unit configured to control to execute first determination processing for determining the object on one of the plurality of image data and the generated combined image data, wherein the control unit switches between execution of the first determination processing on at least one of the plurality of image data and execution of the first determination processing on the combined image data.