A non-contact power transmission device is disclosed. The resonant system includes a primary coil connected to the AC power source, a primary resonance coil, a secondary resonance coil, and a secondary coil is connected to the load. When the relationship between an input impedance of the resonant system and a frequency of an AC voltage of the AC power source is shown in a graph, the frequency of the AC voltage of the AC power source is set between a first frequency at which the input impedance has a local maximum value, and a second frequency that is greater than the first frequency and at which the input impedance has a local minimum value.