A power transmission system include a transfer case including an input shaft, an output shaft, a planetary gear device including a first rotary element, a second rotary element, and a third rotary element, and a HIGH-LOW switching mechanism including a switching sleeve configured to selectively couple the output shaft to the first rotary element and the second rotary element, an electric motor coupled to one of the first rotary element and the second rotary element, and an electronic control unit configured to control the rotational speed of the electric motor, during switching operation of the HIGH-LOW switching mechanism while a vehicle is stopped, such that the rotational speed of the input shaft becomes substantially equal to zero.