A method for controlling a power transmitting device is a method for detecting a metal foreign object by controlling the power transmitting device including a power transmitting coil that outputs power to a power receiving coil and a thermal sensor that measures a surface temperature of the metal foreign object on the power transmitting coil. The method includes causing the power transmitting coil to output the power before the coils are electromagnetically coupled with each other and a mobile object including the power receiving coil overlaps the power transmitting coil, causing the thermal sensor to measure the surface temperature of the metal foreign object, and transmitting, if the measured surface temperature of the metal foreign object is equal to or higher than a threshold, a signal indicating presence of the metal foreign object to another receiving apparatus, other than the power transmitting device, having a function of receiving the signal.