1. An image processing apparatus comprising: a detection unit configured to detect a face area and an eye area from images that are sequentially input; a motion vector calculation unit configured to calculate, between two of the images, a first motion vector in the face area and second motion vectors in a plurality of blocks obtained by dividing the eye area; a similarity calculation unit configured to calculate, for each pair of the images, a value relevant to a similarity between the first motion vector and each of the second motion vectors; and a determination unit configured to determine whether blinking has occurred based on the value relevant to the similarity.