An image forming apparatus includes an image carrier; a movable endless belt member forming a nip between the image carrier; and a transfer roller made of metal contacting the belt member at a region corresponding to the nip. At the nip, a toner image on the image carrier is transferred onto the belt member. The transfer roller slidably rotates in bearings supporting its shaft. Members having a higher friction coefficient than that of the transfer roller are provided at end portions of the transfer roller. F1>F3 and F2>F4 are satisfied, where F1 is a maximum static friction between the transfer roller and the belt member, F2 is a dynamic friction between the transfer roller and the belt member, F3 is a maximum static friction between the shaft of the transfer roller and the bearings, and F4 is a dynamic friction between the shaft of the transfer roller and the bearings.