PROBLEM TO BE SOLVED: To provide a wireless power transmission system capable of attaining high safety.SOLUTION: When it is detected that a medical instrument wearer approaches a vehicle 10, transmission power from a primary coil 35 of a charger 30 to a secondary coil 15 of the vehicle 10 is suppressed. When electric power is wirelessly transmitted, electromagnetic waves may leak between the primary coil 35 and the secondary coil 15 to the outside. The intensity of an electromagnetic wave propagates more highly and widely as the power supplied to the primary coil 35 is higher. For example, when a medical instrument wearer receives electromagnetic waves, it may have an adverse effect upon a medical instrument. According to the present invention, when the medical instrument wearer is present around the vehicle, the transmission power from the primary coil 35 to the secondary coil 15 is suppressed, thereby suppressing the adverse effect of electromagnetic waves upon the medical instrument.