In a power transmission device including a power transmission coil that is disposed to oppose an installation surface of the power transmission device on which a power receiving device is installed and that is capable of being electromagnetically coupled with the power receiving coil. A magnetic substance is disposed at least outside the power transmission coil to oppose the installation surface via the power transmission coil and to be electromagnetically coupled with the power transmission coil. A object detecting circuit detects a metal object existing at least outside the power transmission coil by supplying first AC power to the power transmission coil and detecting a change in at least one of a voltage, a current, and a frequency of the first AC power or a voltage or current of a DC component of the first AC power.