A wall-mounting image processing apparatus (A) includes a machine housing (90) mounted on a substantially vertical wall surface (H), and an image reading/writing head (X) disposed in the machine housing. The image reading/writing head (X) includes a substrate (4) having one surface (4A) on which a plurality of light receiving elements (4a) are arranged in a row. Part of said one surface (4A) forms an excess surface (49) projecting laterally from a head case (1), and the printing elements (4b) are arranged on the excess surface (49).