An image forming apparatus comprising: an apparatus main body ; a drive source ; a first photosensitive member on which an electrostatic latent image is to be formed; a first developing roller configured to supply developer to the first photosensitive member ; a first urging member configured to urge the first developing roller toward the first photosensitive member ; and a translation cam configured to be movable relative to the apparatus main body in a predetermined direction upon receipt of a drive force from the drive source and to move the first developing roller between a first contact position contacting the first photosensitive member and a first retracted position retracted from the first photosensitive member , wherein the translation cam has a first cam surface configured to move the first developing roller from the first contact position to the first retracted position against an urging force of the first urging member and a first holding surface configured to hold the first developing roller at the first retracted position against an urging force of the first urging member , characterized in that the image forming apparatus further comprises an adjacent member which includes a first engaging portion and which is fixed to the apparatus main body so as to be adjacent to the translation cam , the translation cam includes a second engaging portion engageable, in the predetermined direction, with the first engaging portion , and the first engaging portion and the second engaging portion are positioned such that, when the translation cam is moved in the predetermined direction, the first engaging portion and the second engaging portion engages each other to restrict the movement of the translation cam in the predetermined direction before a surface of the translation cam , receiving an urging force from the first urging member , is switched from the first holding surface to the first cam surface , and are configured such that one of the first engaging portion and the second engaging portion does not climb over the other one of the first engaging portion and the second engaging portion when a force smaller than the drive force from the drive source is applied to the translation cam , and the one is deformable or displaceable to climb over the other one to release engagement between the first engaging portion and the second engaging portion when a force equal to or larger than the drive force from the drive source is applied to the translation cam , wherein projections are employed as the first and the second engaging portions , or wherein a projection and a depression is employed as the first and the second engaging portions . an apparatus main body ; a drive source ; a first photosensitive member on which an electrostatic latent image is to be formed; a first developing roller configured to supply developer to the first photosensitive member ; a first urging member configured to urge the first developing roller toward the first photosensitive member ; and a translation cam configured to be movable relative to the apparatus main body in a predetermined direction upon receipt of a drive force from the drive source and to move the first developing roller between a first contact position contacting the first photosensitive member and a first retracted position retracted from the first photosensitive member , wherein the translation cam has a first cam surface configured to move the first developing roller from the first contact position to the first retracted position against an urging force of the first urging member and a first holding surface configured to hold the first developing roller at the first retracted position against an urging force of the first urging member , characterized in that the image forming apparatus further comprises an adjacent member which includes a first engaging portion and which is fixed to the apparatus main body so as to be adjacent to the translation cam , <EOS>