Provided is a power conversion device capable of directly performing a protection operation according to the state of a cooler. A control unit includes: a semiconductor switching element loss calculation unit which calculates a loss in a semiconductor switching element with use of a switching state of the semiconductor switching element, and a current detection value or a voltage detection value; and a cooler state estimation unit which estimates a state of a cooler on the basis of a loss calculation value from the semiconductor switching element loss calculation unit and a temperature detection value from a temperature detector. The control unit limits current flowing to the semiconductor switching element on the basis of the state of the cooler.