To accurately transmit rotation from a driving bevel gear to a driven bevel gear by stably rotating a truncated-cone-shaped base while making it unlikely to vibrate during the rotation since it is not necessary to screw a magnet fixing flange for preventing a permanent magnet from being dropped to the truncated-cone-shaped base like the prior arts.

In a bevel gear device, magnet burying dovetail grooves are formed radially on a conical surface of a pair of mutually opposing truncated-cone-shaped bases of a driving bevel gear and a driven bevel gear, permanent magnets attracting each other are buried in the magnet burying dovetail grooves, and rotation is transmitted from the driving bevel gear to the driven bevel gear. The magnet burying dovetail groove is opened only at an upper edge of the conical surface of the truncated-cone-shaped base, and the permanent magnet is inserted from the upper end opening.