At least one of a plurality of rollers supporting an endless belt includes a flange arranged on an end portion of the roller. The flange includes a cylindrical portion that is inserted into an opening portion of the roller at its end. Outer circumference of the cylindrical portion makes contact with inner circumference of the roller, and inner circumference of the flange makes contact with a rotation shaft of the roller. The inner edge of a surface where the flange is in contact with the rotation shaft is located on the inner side of the outer edge of a surface where the cylindrical portion is in contact with the roller in the longitudinal direction of the rotation shaft.