MOTOR DEVICE

Motor device includes: motor part including armature shaft; speed reduction mechanism which includes worm and worm wheel and outputs the rotation of the armature shaft at reduced speed; gear case which is provided with bottom part and opening part and accommodates the worm and worm wheel in rotatable manner; gear cover which covers the opening part of the gear case; circuit board which is arranged between the speed reduction mechanism and the gear cover; and board cover which is arranged between the circuit board and the speed reduction mechanism. The board cover is provided with positioning protrusion part protruding toward the gear case, the gear case is provided with positioning recess part into which the positioning protrusion part is press-fit, and the bottom surface of the positioning recess part and the tip surface of the positioning protrusion part press-fit into the positioning recess part face each other with gap therebetween.