A power conversion device comprising: an insulated gate type first transistor that controls a main current; an insulated gate type second transistor that is formed on a same semiconductor substrate as the first transistor, is electrically connected with each of a drain and a gate of the first transistor in parallel, and is configured to detect a current of the first transistor; a current measurement circuit that is connected between a source electrode of the second transistor and a source electrode of the first transistor to measure a current flowing through the second transistor, wherein a region of a source of the first transistor is larger than a region of a source of the second transistor; a diode that is formed on the semiconductor substrate and connected between the source electrode of the second transistor and the source electrode of the first transistor; and a temperature measurement circuit that is connected to the source electrode of the second transistor and measures a temperature of the semiconductor substrate by causing a predetermined forward current to flow through the diode when the first transistor is in an off state, wherein a bonding pad formed on the semiconductor substrate on which the first transistor, the second transistor, and the diode are mounted includes a first bonding pad to which a source or emitter electrode of the first transistor and a cathode electrode of the diode are connected, a second bonding pad to which a source or emitter electrode of the second transistor and an anode electrode of the diode are connected, and a third bonding pad to which gate electrodes of the first and second transistors are connected, characterized in that the temperature measurement circuit includes a constant current source that is configured to cause the forward current to flow and a voltage measurement circuit that is configured to measure a source potential of the second transistor, when the first transistor is in the off state, the constant current source is configured to cause a first current value to flow to the diode and is configured to then cause a second current value to flow to the diode, and the voltage measurement circuit is configured to detect a source potential of the second transistor during flow of the first current value and a source voltage of the second transistor during flow of the second current value, calculate a difference value between the source potential and the source voltage, and calculate a temperature of the semiconductor substrate from the difference value. an insulated gate type first transistor that controls a main current; an insulated gate type second transistor that is formed on a same semiconductor substrate as the first transistor, is electrically connected with each of a drain and a gate of the first transistor in parallel, and is configured to detect a current of the first transistor; a current measurement circuit that is connected between a source electrode of the second transistor and a source electrode of the first transistor to measure a current flowing through the second transistor, wherein a region of a source of the first transistor is larger than a region of a source of the second transistor; a diode that is formed on the semiconductor substrate and connected between the source electrode of the second transistor and the source electrode of the first transistor; and a temperature measurement circuit that is connected to the source electrode of the second transistor and measures a temperature of the semiconductor substrate by causing a predetermined forward current to flow through the diode when the first transistor is in an off state, wherein a bonding pad formed on the semiconductor substrate on which the first transistor, the second transistor, and the diode are mounted includes a first bonding pad to which a source or emitter electrode of the first transistor and a cathode electrode of the diode are connected, a second bonding pad to which a source or emitter electrode of the second transistor and an anode electrode of the diode are connected, and a third bonding pad to which gate electrodes of the first and second transistors are connected, characterized in that the temperature measurement circuit includes a constant current source that is configured to cause the forward current to flow and a voltage measurement circuit that is configured to measure a source potential of the second transistor, when the first transistor is in the off state, the constant current source is configured to cause a first current value to flow to the diode and is configured to then cause a second current value to flow to the diode, and the voltage measurement circuit is configured to detect a source potential of the second transistor during flow of the first current value and a source voltage of the second transistor during flow of the second current value, calculate a difference value between the source potential and the source voltage, and calculate a temperature of the semiconductor substrate from the difference value.