A power transmission system according to an embodiment includes a transmitting device and a receiving device. The transmitting (receiving) device includes a transmitting (receiving) housing and a transmitting (receiving) coil. The transmitting (receiving) housing includes a first transmitting (receiving) surface and a second transmitting (receiving) surface. The transmitting (receiving) coil includes a first transmitting (receiving) part and a second transmitting (receiving) part. A first facing area and a second facing area at the reference position are set such that change of strength of magnetic coupling between the transmitting coil and the receiving coil of when the receiving device is moved in a direction perpendicular to the first transmitting surface becomes smaller than change of strength of magnetic coupling between the transmitting coil and the receiving coil of when the receiving device is moved in a direction perpendicular to the second transmitting surface.