A totally enclosed type main drive motor for a vehicle includes a stator core arranged on an inner circumference of an outer casing frame, a bracket arranged on one end of the outer casing frame to have a bearing built-in, a housing arranged on the other end of the outer casing frame to have a bearing built-in, a rotor shaft having its both ends supported by the respective bearings, a rotor core arranged on the rotor shaft, a fan arranged on one end of the rotor shaft, openings formed in both axial ends of a peripheral wall of the outer casing frame, connective air ducts arranged outside the peripheral wall so as to communicate with the openings and a cooler for connecting these connective air ducts with each other and also releasing heat of air flowing in the connective air ducts to outside air. The outer casing frame is attached to the vehicle so that a central axis of the outer casing frame extends horizontally and intersects with a traveling direction of the vehicle at right angles. With rotation of the fan, air inside the outer casing frame flows in the cooler in circulation to cool down the air. The totally enclosed type main drive motor is provided with guide plates that collect traveling wind flowing around the outer casing frame to the cooler.