An image forming apparatus to achieve stable attachment/detachment of a developing device and stable power transmission while preventing contamination of the surroundings due to leakage of developer. The image forming apparatus includes a cover to be opened away from or closed to an upper surface of a body, and a drive device provided at a side of the developing device so as to be coupled with or released from the developing device and be moved in linkage with opening/closing of the cover. The developing device includes driven coupling members to be rotated upon receiving drive power from the drive device. The drive device includes driving coupling members engaged with the driven coupling members, and a moving member to horizontally move the driving coupling members according to the opening/closing of the cover and to control the engagement/disengagement of the driving coupling members and the driven coupling members.