A connection part 30 between brush side terminals 31a to 31c and power side terminal pieces 32a to 32c is disposed either of positions L and R located laterally next to an axis of a motor and opposed to each other with respect to the axis. Both terminals are connected each other through a connection unit 36 ditachably fitted to the brush side terminals 31a and others and the power side terminal pieces 32a and others. The connection unit 36 has male terminals 37a to 37c to be coupled to the brush side terminal 31a and others, female terminals 38a to 38c to be coupled to the power side terminal piece 32a and others, and a coil part for noise prevention connecting the male terminal 37a and others to the female terminal 38a and others. The connection part 30 can be set to the position L or R by rotating the brush holder 15 in circumferential direction, which makes it possible to use the connection unit 36 at any of these positions. Thus, the brush holder unit can be shared in electric motors having speed reduction mechanism with different specifications to reduce a product cost.