Image forming apparatus and image forming method

An image forming apparatus of a tandem method includes a conveying member configured to provide to a recording member a conveying force in a sub-scanning direction, a plurality of image carriers configured to contact the conveying member with an equal interval between contacting portions of the plurality of image carriers and the conveying member, a contact force adjusting mechanism configured to freely adjust a contact force of the conveying member to the plurality of image carriers between a predetermined contact force and a decreased contact force, a plurality of toner image forming devices configured to form toner images of a predetermined pattern on the plurality of image carriers respectively. A length of the pattern in the sub-scanning direction is set shorter than a length of the equal interval. The apparatus also includes transferring devices configured to transfer the toner images on the plurality of image carriers onto the conveying member, respectively; and a contact force changing device configured to change the predetermined contact force to the decreased contact force before respective tips of the toner images on the conveying member pass subsequent contacting portions, so that respective parts of the toner images are not transferred onto subsequent image carriers.