A non-contact power supply system has a conversion circuit that converts power of a power transmission-side power supply, and outputs power to a power transmission coil. A power transmission-side controller controls the conversion circuit. A power reception coil receives power from the power transmission coil in a non-contact manner. The power reception coil supplies power to a load electrically connected to the power reception coil. A smoothing circuit smooths power received by the power reception coil. A sensor detects current or voltage in the smoothing circuit. A power reception-side controller acquires an encoded value from a detection value of the sensor. The power transmission-side controller measures an elapsed time between a previous rise and a current rise in a detection voltage that is detected by the sensor, and compares the elapsed time and an elapsed time threshold that is set in advance to acquire the encoded value.