A foreign matter detection device is mounted on a non-contact power supply system that supplies power in a non-contact manner from a power supply unit to a power reception unit. The foreign matter detection device includes a magnetic field sensor and a magnetic field generation unit. The magnetic field sensor detects an amount of magnetic flux that changes due to foreign matter existing between the power supply unit and the power reception unit. The magnetic field generation unit is provided separately from the power supply unit and the power reception unit, includes a magnetic field generation coil unit, and generates a magnetic field for driving the magnetic field sensor.