A connection structure between a reduction or step-up gear and a motor is divided in two parts. Various kinds of reduction or step-up gears and motors can be mated to each other by means of one kind or a few kinds of divided bodies, to obtain the standard product group. Specifically, the structure connecting a reduction or step-up gear to a motor is divided into a gear-side flange part (34a) and a motor mounting plate (34b). With this construction, plural kinds of reduction or step-up gears can be mounted on one kind of gear-side flange part (34a), and plural kinds of motors (16) can be mounted on one kind of the motor mounting plate (34b). <IMAGE>
