PURPOSE: To shorten the time necessary for forming an image in a monochrome mode by providing a supporting means which selectively positions either of a transfer paper holding body provided with a transfer paper clamping mechanism which is used in a color mode and a transfer roller which is used in the monochrome mode to a transfer acting position.

CONSTITUTION: By rotating an arm member 27 counterclockwise from a state where the transfer roller 24 is opposed to the surface of a photosensitive drum 6, a transfer drum 23 can be opposed to the surface of the drum 6. On the contrary, by rotating the member 27 clockwise from the above state, the roller 24 can be opposed to the surface of the drum 6. Then, a 1st carrying belt device 32 to which a separation pawl 34 is attached and a 2nd carrying belt device 33 are moved by a driving mechanism synchronizing with the rotation of the member 27 between a state where the separation pawl 34 is opposed to the surface of the roller 24 which is opposed to the surface of the drum 6 and a state where the pawl 34 is opposed to the vicinity of a separation discharger 30 on the surface of the drum 23.