A method for detecting a metal foreign object using a power transmission device, the power transmission device including: an inverter that generates power; a power transmitting coil for outputting power to a power receiving coil included in a mobile object; a thermal sensor for measuring a temperature distribution in a target area located around the power transmitting coil; and a power transmission control circuitry configured to cause the inverter to control the power output from the power transmitting coil; the method comprising the step of causing the power transmission control circuitry to: cause the power transmitting coil to output the power before the power receiving coil and the power transmitting coil are electromagnetically coupled with each other and the mobile object overlaps the power transmitting coil, which increases the temperature of a metal foreign object potentially located around the power transmitting coil; cause the thermal sensor to measure a temperature distribution in the target area; characterized in that the method further comprises the steps of: transmitting, if a temperature measured in the target area is equal to or higher than a threshold, information indicating a relative positional relationship between the power transmitting coil and the metal foreign object on the basis of the measured temperature distribution; and transmitting information indicating a relative positional relationship between the power transmitting coil and the detected metal foreign object to a receiving apparatus. an inverter that generates power; a power transmitting coil for outputting power to a power receiving coil included in a mobile object; a thermal sensor for measuring a temperature distribution in a target area located around the power transmitting coil; and a power transmission control circuitry configured to cause the inverter to control the power output from the power transmitting coil; the method comprising the step of causing the power transmission control circuitry to: cause the power transmitting coil to output the power before the power receiving coil and the power transmitting coil are electromagnetically coupled with each other and the mobile object overlaps the power transmitting coil, which increases the temperature of a metal foreign object potentially located around the power transmitting coil; cause the thermal sensor to measure a temperature distribution in the target area; characterized in that the method further comprises the steps of: transmitting, if a temperature measured in the target area is equal to or higher than a threshold, information indicating a relative positional relationship between the power transmitting coil and the metal foreign object on the basis of the measured temperature distribution; and transmitting information indicating a relative positional relationship between the power transmitting coil and the detected metal foreign object to a receiving apparatus. cause the power transmitting coil to output the power before the power receiving coil and the power transmitting coil are electromagnetically coupled with each other and the mobile object overlaps the power transmitting coil, which increases the temperature of a metal foreign object potentially located around the power transmitting coil; cause the thermal sensor to measure a temperature distribution in the target area; characterized in that the method further comprises the steps of: transmitting, if a temperature measured in the target area is equal to or higher than a threshold, information indicating a relative positional relationship between the power transmitting coil and the metal foreign object on the basis of the measured temperature distribution; and transmitting information indicating a relative positional relationship between the power transmitting coil and the detected metal foreign object to a receiving apparatus. transmitting, if a temperature measured in the target area is equal to or higher than a threshold, information indicating a relative positional relationship between the power transmitting coil and the metal foreign object on the basis of the measured temperature distribution; and transmitting information indicating a relative positional relationship between the power transmitting coil and the detected metal foreign object to a receiving apparatus.