An image forming apparatus for forming an image on a recording material is constituted by an image bearing member, a driving source, a first pulley rotatable by actuation of the driving source, a second pulley, connected to a rotatable member, for transmitting rotation of the driving source to the image bearing member, a belt supported by the first pulley and the second pulley, a first pressing member which is disposed upstream from the first pulley with respect to a rotational direction of the drum and located closer to the second pulley than a rotation axis of the first pulley so as to press the first pulley through the belt, and a second pressing member disposed at a position substantially symmetrically opposite from the first pressing member with respect to a line connecting the rotation axis of the first pulley and a rotation axis of the second pulley so as to press the first pulley through the belt.