A ground-side coil device includes a ground-side coil disposed on a road surface where a vehicle parks or stops and transmitting or receiving, via a magnetic field, electric power to or from a vehicle-side coil mounted on the vehicle, a position detection sensor disposed around the ground-side coil and acquiring information relating to the position, relative to the ground-side coil, of the vehicle approaching the ground-side coil, a screen disposed at a position visible to a driver of the vehicle approaching the ground-side coil, and a control unit controlling a display mode on the screen.