1. An image processing apparatus for processing input image data that corresponds to a pixel area in order to perform printing in the pixel area by a plurality of relative movement including a first relative movement and a second relative movement of a print unit with respect to a printing medium, comprising: a generation unit configured to generate, based on the input image data, first multi-valued image data that corresponds to the first relative movement and second multi-valued image data that corresponds to the second relative movement; and a quantization unit configured to perform quantization processing of the second multi-valued image data based on the first multi-valued image data, and perform quantization processing of the first multi-valued image data based on the second multi-valued image data.