[Problem] To easily detect the phase difference between voltage and current.
[Solution] A voltage conversion device of an embodiment of the present invention is provided with a DC power supply unit for generating a DC voltage, an inverter, an AC component detection unit, and a phase estimation unit. The inverter has a first end electrically connected to one of the positive and negative side terminals of the DC power supply unit and a second end electrically connected to the other of the positive and negative side terminals, and generates an AC power on the basis of the DC voltage. The AC component detection unit detects an AC component of the current flowing through the first end or the second end. The phase estimation unit estimates a phase relationship between the voltage phase of the AC power and the current phase of the AC power on the basis of the amplitude of a specific frequency component included in the absolute value signal of the AC component. The voltage conversion device supplies the AC power to a load device. The impedance of the load device at the fundamental wave of the driving frequency of the inverter is smaller than the impedance of the load device at odd-order harmonics of the driving frequency.