A non-contact power transmission device comprising: a primary device including a primary coil configured to receive alternating current power; and a secondary device including a secondary coil that is configured to receive the alternating current power from the primary coil in a non-contact manner, a rectifier configured to rectify alternating current power, which is received by the secondary coil, to direct current power, a load, a matching unit that is located between the secondary coil and the rectifier and has a predetermined fixed inductance and a predetermined fixed capacitance, and an adjustment unit that includes a switching element ( 31, 32) configured to perform a switching operation in a predetermined cycle, wherein the adjustment unit is configured to adjust a duty ratio of the switching operation in accordance with an impedance of the load, wherein the adjustment unit includes a DC/DC converter configured to adjust the duty ratio to convert a voltage of direct current power, which has been rectified by the rectifier, to a voltage of a different level and output the voltage of the different level to the load, and wherein the adjustment unit is configured to adjust the duty ratio so that the impedance from an output terminal of the matching unit to the load is constant regardless of the impedance of the load; characterised in that the secondary device further includes: a resistor connected in parallel to the DC/DC converter and the load, and a switch configured to switch an output terminal of the rectifier between the DC/DC converter and the resistor, wherein a resistance of the resistor is set to be the same as an impedance from the output terminal of the rectifier to the load. a primary device including a primary coil configured to receive alternating current power; and a secondary device including a secondary coil that is configured to receive the alternating current power from the primary coil in a non-contact manner, a rectifier configured to rectify alternating current power, which is received by the secondary coil, to direct current power, a load, a matching unit that is located between the secondary coil and the rectifier and has a predetermined fixed inductance and a predetermined fixed capacitance, and an adjustment unit that includes a switching element ( 31, 32) configured to perform a switching operation in a predetermined cycle, wherein the adjustment unit is configured to adjust a duty ratio of the switching operation in accordance with an impedance of the load, wherein the adjustment unit includes a DC/DC converter configured to adjust the duty ratio to convert a voltage of direct current power, which has been rectified by the rectifier, to a voltage of a different level and output the voltage of the different level to the load, and wherein the adjustment unit is configured to adjust the duty ratio so that the impedance from an output terminal of the matching unit to the load is constant regardless of the impedance of the load; characterised in that the secondary device further includes: a resistor connected in parallel to the DC/DC converter and the load, and a switch configured to switch an output terminal of the rectifier between the DC/DC converter and the resistor, wherein a resistance of the resistor is set to be the same as an impedance from the output terminal of the rectifier to the load. a resistor connected in parallel to the DC/DC converter and the load, and a switch configured to switch an output terminal of the rectifier between the DC/DC converter and the resistor, wherein a resistance of the resistor is set to be the same as an impedance from the output terminal of the rectifier to the load.