A developing device usable with an electrophotographic image forming apparatus includes a driving shaft having a rotating force applying portion, and a movable member. The developing device is mounted to the moving member and includes a developing roller, and a coupling member that includes a rotating force receiving portion and a rotating force applying portion. The coupling member is capable of taking (i) a rotational force transmitting angular position for transmitting the rotational force to the developing roller, (ii) a pre-engagement angular position taken before the coupling member is engaged with the rotating force applying portion, in which the coupling member is inclined away from the rotational force transmitting angular position, and (iii) a disengaging angular position, which enables the coupling member to disengage from the driving shaft, and inclines the coupling member away from the rotational force transmitting angular position, in a direction opposite to the pre-engagement angular position.