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 conveyer driving device includes a permanent magnet synchronous motor 3 that rotates and drives a driving shaft 2 of a conveyer 1 in a direct-drive method. The permanent magnet synchronous motor 3 is energized in such a manner that the current has a leading phase relative to induced voltages in windings of respective phases thereof. Thus, the permanent magnet synchronous motor 3 is configured so as to have constant torque within a predetermined rotation speed range.