A wireless power transmitting device, comprising: a charging module configured to transmit a foreign object sensing signal for sensing at least one of a wireless power receiving device and a foreign object on a charging pad of the wireless power transmitting device, and transmit a wireless power signal for charging the wireless power receiving device; and a control module configured to: sense output voltage (Vout) from the charging module based on transmitting the foreign object sensing signal; and sense at least one of the foreign object and the wireless power receiving device based on the sensed output voltage (Vout), wherein the charging module comprises: a transmitting unit configured to transmit the wireless power signal by resonating a resonance value of a transmitting coil included in the transmitting unit at a first resonance value corresponding to the wireless power signal; and a resonance converting unit, characterized in that the resonance converting unit further comprises: a switch configured to switch on and switch off to transmit the wireless power signal or the foreign object sensing signal, based on controlling by the control module, wherein, when the switch is on, the switch delivers driving power that is output from an inverter unit to the transmitting unit, and a variable capacitor that is connected with the switch in parallel and that is configured to, when the switch switches off, vary the first resonance value of the transmitting coil into a second resonance value to transmit the foreign object sensing signal, in which a frequency of the driving power is varied, through the transmitting unit. a charging module configured to transmit a foreign object sensing signal for sensing at least one of a wireless power receiving device and a foreign object on a charging pad of the wireless power transmitting device, and transmit a wireless power signal for charging the wireless power receiving device; and a control module configured to: sense output voltage (Vout) from the charging module based on transmitting the foreign object sensing signal; and sense at least one of the foreign object and the wireless power receiving device based on the sensed output voltage (Vout), sense output voltage (Vout) from the charging module based on transmitting the foreign object sensing signal; and sense at least one of the foreign object and the wireless power receiving device based on the sensed output voltage (Vout), wherein the charging module comprises: a transmitting unit configured to transmit the wireless power signal by resonating a resonance value of a transmitting coil included in the transmitting unit at a first resonance value corresponding to the wireless power signal; and a resonance converting unit, a transmitting unit configured to transmit the wireless power signal by resonating a resonance value of a transmitting coil included in the transmitting unit at a first resonance value corresponding to the wireless power signal; and a resonance converting unit, a switch configured to switch on and switch off to transmit the wireless power signal or the foreign object sensing signal, based on controlling by the control module, wherein, when the switch is on, the switch delivers driving power that is output from an inverter unit to the transmitting unit, and a variable capacitor that is connected with the switch in parallel and that is configured to, when the switch switches off, vary the first resonance value of the transmitting coil into a second resonance value to transmit the foreign object sensing signal, in which a frequency of the driving power is varied, through the transmitting unit.