Nozzles for ejecting color ink are aligned in the conveying direction of a recording sheet at a pitch corresponding to three times the pitch of nozzles ejecting black ink. A region in which an image is printed is divided into sixteen regions segmented into four parts in the scanning and conveying directions. Each region includes eight dots in the scanning direction and four dots in the conveying direction. With respect to regions which include one character, in one side attachment regions, black ink is ejected only when an ink jet head is moved to the right side. With respect to regions which include one character, in the other side attachment regions, black ink is ejected only when the ink jet head is moved to the left side.