To provide a conveyer driving device that reduces component count and thereby delivery time and costs and that improves efficiency and thereby saves energy, is made compact, and has an improved outward appearance.

A permanent magnet synchronous motor 3 rotates and drives a driving shaft 2 of a conveyer 1 in a direct-drive method. The permanent magnet synchronous motor 3 is a variable magnetic flux motor 3a that has variable magnets as low-coercive-force permanent magnets. Magnetizing current is supplied to the variable magnets according to the rotation speed so as to control magnetic flux. Thus, the variable magnetic flux motor 3a is configured so as to have constant torque within a predetermined rotation speed range.