1. An image processing apparatus which corrects a captured image obtained by capturing an object, the apparatus comprising: an acquiring unit configured to acquire, for each pixel of the captured image, information on an object distance representing a distance to the object; a calculating unit configured to calculate, based on the information on the object distance, a difference in the object distance between a pixel of interest in the captured image and a surrounding pixel of the pixel of interest; a parameter setting unit configured to set a sharpening process parameter for the pixel of interest based on the calculated difference in the object distance; and a sharpening process unit configured to perform a sharpening process for the pixel of interest by using the set parameter.