There is provided a wireless power transmitting device which can detect relative positions of a power transmitting coil and a power receiving coil with a simple configuration, and reduce cost of components. The wireless power transmitting device has: a power transmitting coil which supplies power to a power receiving coil by way of electromagnetic induction; an excitation coil which excites the power receiving coil; a plurality of detecting coils which are arranged around a center of the power transmitting coil; and notifying units, and each of the detecting coils has a shape which widens apart from the center of the power transmitting coil, and the notifying units notify relative positions of the power transmitting coil and the power receiving coil by detecting an echo signal produced in the power receiving coil through the plurality of detecting coils.