A wireless power transmission system includes a receiver and a transmitter. The transmitter includes: a power transmission unit that transmits power; a power adjustment unit that adjusts power to be transmitted; and a communication unit. The receiver includes: a power receiving unit that receives power; a power detection unit that detects the received power; a power storage unit that stores the received power; and a communication unit. The power to be transmitted is adjusted on the basis of power transmission efficiency and the remaining energy storage level. The power transmission efficiency is the ratio between the transmitted power and the received power.