A power transmission control device provided in a power transmitting device of a non-contact power transmission system includes a driver control circuit that controls a power transmitting driver that drives a primary coil, a load state detection circuit that detects a power-receiving-side load state, and a control circuit that controls the power transmission control device. The control circuit acquires a reference value used to determine a power-receiving-side load state after starting normal power transmission in a reference value acquisition period, the reference value acquisition period being a period after receiving ID authentication information from the power receiving device, but before starting the normal power transmission.