In a color printer having plural photosensitive drums for respective recording color components, when images are continuously formed on recording sheets, lengths of image data of one page in its main scan direction and its sub scan direction are held for plural pages. Then, image data writing and reading addresses to and from a delay memory for delaying the image data according to an inter-drum distance are controlled for each page on the basis of the held lengths of the image data in its main scan direction and its sub scan direction, whereby an interval between the successively transported recording sheets is shortened.