To provide a belt conveyor capable of correcting a belt shift without adding a regulation means, and capable of contributing remarkably to compactifying a device and reducing cost thereof.

Supply of a transfer paper sheet S2 is stopped and only a transfer paper sheet S1 is supplied when a belt 23c is shifted to a left side because of a difference of restriction force, in constitution for supplying the transfer paper sheets S1, S2 different in sizes in parallel to be conveyed in parallel by a transfer belt 23. The supply is restored to the parallel conveyance when the shift of the belt 23c is confirmed to be restored by a belt shift detecting sensor 26.