An electric motor apparatus comprising an electric motor which is driven by power supplied thereto, a motive-power transmission mechanism (14, 22, 23) to which motive power is transmitted from the electric motor, and a housing in which the motive-power transmission mechanism and part of the electric motor are accommodated, the electric motor including: an armature shaft which is partially housed in the housing, and rotatable about an axis thereof; a coil which is installed to the armature shaft; a commutator which is installed to the armature shaft and switches a current flowing in the coil; and a cylindrical yoke which is fixed to the housing the electric motor having a portion located outside the housing and accommodated in the yoke, and a brush holder holding a power supply brush (26c, 26d) which comes into contact with the commutator and a connector unit which is conductively connected to the brush and to which an external connector is detachably connected, characterized in that: the housing includes: a concave portion having a first opening portion opened in a plane parallel to the axis; a holding portion formed with a holding hole having a second opening portion opened in a plane perpendicular to the axis; and an accommodation chamber having a third opening portion opened in a plane parallel to the first opening portion, and communicating with the holding hole, the connector unit is installed to the concave portion through the first opening portion, and the brush holder is installed to the holding hole through the second opening portion so that the brush and the connector unit are conductively connected to each other, the armature shaft has a portion which is accommodated in the accommodation chamber through the holding hole, the motive-power transmission mechanism is accommodated in the accommodation chamber through the third opening portion, and the yoke is fixed to the housing so as to cover the second opening portion. the electric motor including: an armature shaft which is partially housed in the housing, and rotatable about an axis thereof; a coil which is installed to the armature shaft; a commutator which is installed to the armature shaft and switches a current flowing in the coil; and a cylindrical yoke which is fixed to the housing the electric motor having a portion located outside the housing and accommodated in the yoke, and a brush holder holding a power supply brush (26c, 26d) which comes into contact with the commutator and a connector unit which is conductively connected to the brush and to which an external connector is detachably connected, characterized in that: the housing includes: a concave portion having a first opening portion opened in a plane parallel to the axis; a holding portion formed with a holding hole having a second opening portion opened in a plane perpendicular to the axis; and an accommodation chamber having a third opening portion opened in a plane parallel to the first opening portion, and communicating with the holding hole, the connector unit is installed to the concave portion through the first opening portion, and the brush holder is installed to the holding hole through the second opening portion so that the brush and the connector unit are conductively connected to each other, the armature shaft has a portion which is accommodated in the accommodation chamber through the holding hole, the motive-power transmission mechanism is accommodated in the accommodation chamber through the third opening portion, and the yoke is fixed to the housing so as to cover the second opening portion. the housing includes: a concave portion having a first opening portion opened in a plane parallel to the axis; a holding portion formed with a holding hole having a second opening portion opened in a plane perpendicular to the axis; and an accommodation chamber having a third opening portion opened in a plane parallel to the first opening portion, and communicating with the holding hole, the connector unit is installed to the concave portion through the first opening portion, and the brush holder is installed to the holding hole through the second opening portion so that the brush and the connector unit are conductively connected to each other, the armature shaft has a portion which is accommodated in the accommodation chamber through the holding hole, the motive-power transmission mechanism is accommodated in the accommodation chamber through the third opening portion, and the yoke is fixed to the housing so as to cover the second opening portion. a concave portion having a first opening portion opened in a plane parallel to the axis; a holding portion formed with a holding hole having a second opening portion opened in a plane perpendicular to the axis; and an accommodation chamber having a third opening portion opened in a plane parallel to the first opening portion, and communicating with the holding hole, the connector unit is installed to the concave portion through the first opening portion, and the brush holder is installed to the holding hole through the second opening portion so that the brush and the connector unit are conductively connected to each other, the armature shaft has a portion which is accommodated in the accommodation chamber through the holding hole, the motive-power transmission mechanism is accommodated in the accommodation chamber through the third opening portion, and the yoke is fixed to the housing so as to cover the second opening portion.