A contactless power transmission device includes a switching unit that switches a power transmission line so that a first power is transmitted through the first line when an AC power supply outputs a first AC power and so that a second power is transmitted through a second line when the AC power supply outputs a second AC power. An impedance conversion unit is arranged on the second line that converts an impedance from an output of the AC power supply to a variable load when the second power is transmitted through the second line to approach an impedance from the output of the AC power supply to the variable load when the first power is transmitted through the first line.