Motor device and method for manufacturing same

A manufacturing method of a motor device for decelerating and outputting rotation of an armature shaft, wherein the motor device comprises:

• a worm rotated by the armature shaft;
• a worm wheel having teeth meshed with the worm;
• a case made of resin and accommodating the worm and the worm wheel;
• a support shaft made of steel and rotatably supporting the worm wheel;
• a large-diameter part provided on an axial base end side of the support shaft;
• a small-diameter part provided on an axial tip end side of the support shaft and having a smaller diameter than the large-diameter part by drawing;
• and
• a step part provided between the large-diameter part and the small-diameter part of the support shaft,
• wherein the large-diameter part and the step part are embedded in the case, and the small-diameter part is exposed outside the case, and
• the small-diameter part is formed through a drawing process which presses a round bar made of steel and set in a die from an axial direction to push an axial tip end side of the round bar into a small-diameter part molding recess provided in the die and make an external diameter of the small-diameter part smaller than an external diameter of the large-diameter part.