A motor power device for wheelchairs of disabled users is removably mounted on the front of the wheelchair-in order to be controlled by the user while sitting on the wheelchair. The device has a motor unit provided with an electrical motor, an intermediate frame disposed between the motor unit and the wheelchair, first inclination adjusting means between the motor unit and the intermediate frame and second inclination adjusting means between the intermediate frame and a bearing frame of the wheelchair. The intermediate frame and the motor unit are mounted and dismounted easily and rapidly.