A power supply device comprising: a power conversion unit adapted to convert input power into a first power; a wireless power supply unit adapted to vary a switching frequency for switching the first power and to wirelessly transmit the switched first power at a resonance frequency which is determined by the switching frequency; and a controller adapted to vary the switching frequency according to feedback information of the power wirelessly transmitted by the wireless power supply unit and adapted to select one of a plurality of resonance frequency bands, wherein the wireless power supply unit comprises a switching unit comprising a first half bridge switch adapted to switch the first power at a first switching frequency and a second half bridge switch adapted to switch the first power at a second switching frequency, and a resonance unit having a first power transmission coil (Lr), a first capacitor (Cr-WPC) and a second capacitor (Cr-A4WP) and being adapted to resonate at at least one of a first resonance frequency and a second resonance frequency according to switching of the switching unit and to wirelessly transmit the switched first power, wherein said first resonance frequency is determined by the power transmission coil (Lr) and the first capacitor (Cr-WPC) and said second resonance frequency is determined by the power transmission coil (Lr) and the second capacitor (Cr-A4WP), wherein the controller is adapted to control switching of the switching unit in a switching control operation when the first half bridge switch and the second half bridge switch operate separately so that the first capacitor (Cr-WPC) and the power transmission coil (Lr) resonate according to the first switching frequency of the first half bridge switch to wirelessly transmit the switched first power through the first power transmission coil (Lr) at the first resonance frequency, and the second capacitor (Cr-A4WP) and the power transmission coil (Lr) resonate according to the second switching frequency of the second half bridge switch to wirelessly transmit the switched first power through the first power transmission coil (Lr) at the second resonance frequency. a power conversion unit adapted to convert input power into a first power; a wireless power supply unit adapted to vary a switching frequency for switching the first power and to wirelessly transmit the switched first power at a resonance frequency which is determined by the switching frequency; and a controller adapted to vary the switching frequency according to feedback information of the power wirelessly transmitted by the wireless power supply unit and adapted to select one of a plurality of resonance frequency bands, wherein the wireless power supply unit comprises a switching unit comprising a first half bridge switch adapted to switch the first power at a first switching frequency and a second half bridge switch adapted to switch the first power at a second switching frequency, and a resonance unit having a first power transmission coil (Lr), a first capacitor (Cr-WPC) and a second capacitor (Cr-A4WP) and being adapted to resonate at at least one of a first resonance frequency and a second resonance frequency according to switching of the switching unit and to wirelessly transmit the switched first power, a first half bridge switch adapted to switch the first power at a first switching frequency and a second half bridge switch adapted to switch the first power at a second switching frequency, and a resonance unit having a first power transmission coil (Lr), a first capacitor (Cr-WPC) and a second capacitor (Cr-A4WP) and being adapted to resonate at at least one of a first resonance frequency and a second resonance frequency according to switching of the switching unit and to wirelessly transmit the switched first power, wherein said first resonance frequency is determined by the power transmission coil (Lr) and the first capacitor (Cr-WPC) and said second resonance frequency is determined by the power transmission coil (Lr) and the second capacitor (Cr-A4WP), wherein the controller is adapted to control switching of the switching unit in a switching control operation when the first half bridge switch and the second half bridge switch operate separately so that the first capacitor (Cr-WPC) and the power transmission coil (Lr) resonate according to the first switching frequency of the first half bridge switch to wirelessly transmit the switched first power through the first power transmission coil (Lr) at the first resonance frequency, and the second capacitor (Cr-A4WP) and the power transmission coil (Lr) resonate according to the second switching frequency of the second half bridge switch to wirelessly transmit the switched first power through the first power transmission coil (Lr) at the second resonance frequency.