An image processing apparatus obtains a motion vector between at least three images including first, second, and third images obtained through continuous shooting under different exposure conditions and computes a first motion vector between the first and second images and a second motion vector between the first and third images in a plurality of positions on the first image. A reliability level of the motion vector is determined, and an estimated motion vector between the first and second images is computed for the first motion vector having low reliability based on the second motion vector computed in the corresponding position and the shooting interval between the images. In a case where the second motion vector computed in a position corresponding to that of the first motion vector having low reliability has high reliability, the first motion vector having low reliability is substituted with the estimated motion vector.