A snubber circuit unit for a power semiconductor module including an arm having two power semiconductor elements (Q1, Q2) capable of switching which are connected in series, the power semiconductor module including a positive DC input terminal, a negative DC input terminal, and an output terminal which are electrically connected to the arm, the positive DC input terminal, the negative DC input terminal, and the output terminal being provided on an upper surface opposite to an installation surface of the power semiconductor module, the snubber circuit unit comprising: a circuit board; and a plurality of electronic components (R, C, D) mounted on the circuit board, wherein the circuit board includes: a bare board configured to be erected with respect to the upper surface of the power semiconductor module; a conductor layer (122a, 122b) provided on at least one surface of a front surface and a rear surface of the bare board, and forming a first circuit pattern between the positive DC input terminal and the output terminal, and a second circuit pattern between the negative DC input terminal and the output terminal; and a plurality of connection terminals (123, 124, 125) for connecting the conductor layer (122a, 122b) to the positive DC input terminal, the negative DC input terminal, and the output terminal; characterised in that the bare board includes: a pair of insulating substrates (140, 141); and a plurality of conductive substrates (143, 144, 145) sandwiched between the pair of insulating substrates (140, 141) in a state insulated from one another and connected to the conductor layer (122a, 122b) respectively via a through hole (H1, H2, H3), wherein each of the plurality of conductive substrates (143, 144, 145) includes an extended portion (146, 147, 148) protruding from one side surface of the bare board, and wherein the plurality of connection terminals (123, 124, 125) are respectively formed by the extended portions (146, 147, 148) of the plurality of conductive substrates (143, 144, 145). the power semiconductor module including a positive DC input terminal, a negative DC input terminal, and an output terminal which are electrically connected to the arm, the positive DC input terminal, the negative DC input terminal, and the output terminal being provided on an upper surface opposite to an installation surface of the power semiconductor module, the snubber circuit unit comprising: a circuit board; and a plurality of electronic components (R, C, D) mounted on the circuit board, a circuit board; and a plurality of electronic components (R, C, D) mounted on the circuit board, wherein the circuit board includes: a bare board configured to be erected with respect to the upper surface of the power semiconductor module; a conductor layer (122a, 122b) provided on at least one surface of a front surface and a rear surface of the bare board, and forming a first circuit pattern between the positive DC input terminal and the output terminal, and a second circuit pattern between the negative DC input terminal and the output terminal; and a plurality of connection terminals (123, 124, 125) for connecting the conductor layer (122a, 122b) to the positive DC input terminal, the negative DC input terminal, and the output terminal; characterised in that the bare board includes: a pair of insulating substrates (140, 141); and a plurality of conductive substrates (143, 144, 145) sandwiched between the pair of insulating substrates (140, 141) in a state insulated from one another and connected to the conductor layer (122a, 122b) respectively via a through hole (H1, H2, H3), a bare board configured to be erected with respect to the upper surface of the power semiconductor module; a conductor layer (122a, 122b) provided on at least one surface of a front surface and a rear surface of the bare board, and forming a first circuit pattern between the positive DC input terminal and the output terminal, and a second circuit pattern between the negative DC input terminal and the output terminal; and a plurality of connection terminals (123, 124, 125) for connecting the conductor layer (122a, 122b) to the positive DC input terminal, the negative DC input terminal, and the output terminal; characterised in that the bare board includes: a pair of insulating substrates (140, 141); and a plurality of conductive substrates (143, 144, 145) sandwiched between the pair of insulating substrates (140, 141) in a state insulated from one another and connected to the conductor layer (122a, 122b) respectively via a through hole (H1, H2, H3), a pair of insulating substrates (140, 141); and a plurality of conductive substrates (143, 144, 145) sandwiched between the pair of insulating substrates (140, 141) in a state insulated from one another and connected to the conductor layer (122a, 122b) respectively via a through hole (H1, H2, H3), wherein each of the plurality of conductive substrates (143, 144, 145) includes an extended portion (146, 147, 148) protruding from one side surface of the bare board, and wherein the plurality of connection terminals (123, 124, 125) are respectively formed by the extended portions (146, 147, 148) of the plurality of conductive substrates (143, 144, 145).