A wireless power transmitting device that is adapted to wirelessly transmit power to a power receiving device, comprising: an oscillation circuit; a detection circuit that is adapted to detect at least one of an oscillation frequency of the oscillation circuit and an output voltage of the oscillation circuit; a control circuit that is adapted to detect a degree to which the power receiving device approaches the detection resonator, based on a result of a detection performed by the detection circuit; a detection transmitter resonator comprising a resonator (C1, L1); a power transmission circuit that is connected to the resonator (C1, L1) including a capacitor and a detection coil and that is adapted to output AC power to the resonator (C1, L1) for transmitting power; characterized by a first switch (S1, S2) that is adapted to switch a conduction state of a current between the resonator (C1, L1) and the oscillation circuit; and wherein the control circuit is further adapted to switch a mode between an alignment mode in which the first switch (S1, S2) is turned on to connect the oscillation circuit and the resonator (C1, L1) and a power transmission mode in which the first switch (S1, S2) is turned off to disconnect the oscillation circuit from the resonator (C1, L1); wherein the detection transmitter resonator further comprises an inductor and a second switch that is adapted to switch a conduction state of a current from an output of the oscillation circuit to the inductor, and wherein the detection circuit is further adapted for detecting whether an approaching object is the power receiving coil or not based on a change in the oscillation frequency when the second switch is in one of an on-state and an off-state and the first switch (S1, S2) is in an on state, and for detecting the degree to which the power receiving coil approaches based on a change in the oscillation frequency when the second switch is in the other state and the first switch (S1, S2) is in the on state. an oscillation circuit; a detection circuit that is adapted to detect at least one of an oscillation frequency of the oscillation circuit and an output voltage of the oscillation circuit; a control circuit that is adapted to detect a degree to which the power receiving device approaches the detection resonator, based on a result of a detection performed by the detection circuit; a detection transmitter resonator comprising a resonator (C1, L1); a power transmission circuit that is connected to the resonator (C1, L1) including a capacitor and a detection coil and that is adapted to output AC power to the resonator (C1, L1) for transmitting power; characterized by a first switch (S1, S2) that is adapted to switch a conduction state of a current between the resonator (C1, L1) and the oscillation circuit; and wherein the control circuit is further adapted to switch a mode between an alignment mode in which the first switch (S1, S2) is turned on to connect the oscillation circuit and the resonator (C1, L1) and a power transmission mode in which the first switch (S1, S2) is turned off to disconnect the oscillation circuit from the resonator (C1, L1); wherein the detection transmitter resonator further comprises an inductor and a second switch that is adapted to switch a conduction state of a current from an output of the oscillation circuit to the inductor, and wherein the detection circuit is further adapted for detecting whether an approaching object is the power receiving coil or not based on a change in the oscillation frequency when the second switch is in one of an on-state and an off-state and the first switch (S1, S2) is in an on state, and for detecting the degree to which the power receiving coil approaches based on a change in the oscillation frequency when the second switch is in the other state and the first switch (S1, S2) is in the on state.