PURPOSE: To provide a belt conveyor device which is simply and easily assembled and in which zigzag motion is hard to occur on a carrier-side belt side or on the carrier-side belt and return sides.

CONSTITUTION: Three or swore rollers 13 for detachably supporting the carrier- side belt 12a of a belt conveyor in a trough-like form are turnably connected to each other through an adjustable joint to form a carrier roller 5 and at the same time two or are rollers 19 for detachably supporting the return-side belt 12b of the belt conveyor are connected to each other through an adjustable joint to form a return roller 8. Both ends of the carrier roller 5 and the return roller are rockably mounted to the respective fixing systems (upper side member 2).