A processing apparatus processes input pixel data by referring to pixel data of peripheral pixels. The processing apparatus divides an input image in a first direction, inputs pixel data of a divided image divided in the first direction in a second direction crossing the first direction at a right angle, and stores the inputted pixel data. When a pixel to be referred to for processing the stored pixel data is not included in the divided image, the processing apparatus outputs pixel data of the reference pixel based on the stored pixel data, and processes the stored pixel data by referring to the pixel data of the reference pixel.