A method of transferring a plurality of toner images formed on a plurality of image carriers of different colors onto a sheet-type recording medium includes forming a mark image for adjusting a transfer position on each of the image carriers as a toner image; transferring the mark images to a common transfer medium; detecting optically a mutual positional relationship between the mark images; and controlling linear velocities of the image carriers based on a result of detecting the mutual positional relationship between the mark images, to transfer the toner images onto the sheet-type recording medium with a reduced misalignment between the toner images.