Abstract: Even in a case where a power receiving apparatus during wireless power supply is connected to an AC power supply or an apparatus cannot be immediately used after charging due to the occurrence of an error, if wireless power supply is performed, such wireless power supply is inefficient. An embodiment of this invention is made to solve this drawback. Depending on the presence/absence of the connection between the power receiving apparatus and the AC power supply, or depending on an error state of the power receiving apparatus, charging or relay of power from the power transmission apparatus is changed over. This makes it possible to efficiently supply power from the power transmission apparatus depending on the state of the power receiving apparatus.