A can printing apparatus 1 includes a main printer 2 having plural plate cylinders 47 for printing different colors and performing printing onto side surfaces of cans, a secondary printer 6 performing additional printing to the side surfaces of the cans after the printing by the main printer, and a can inspection machine 5 inspecting a printing state. The can inspection machine 5 includes a can rotation device 51 which rotates cans C, a can imaging device 52 which takes images of the cans C and an image processing device 53 which processes the taken images, and the secondary printer 6 includes a printing head 6a which faces a side surface of a can held by the can rotation device 51 of the can inspection machine 5 and a processing unit which gives an instruction of printing to the printing head 6a based on a predetermined printing pattern and processing data of the image processing device 53 of the can inspection machine 5.