A power conversion device which is a test target performs DC voltage conversion between a primary side DC terminal and a secondary side DC terminal. A first connection member electrically connects a testing power supply and the primary side DC terminal serving as an input side of the test target. A second connection member electrically connects the primary side DC terminal and the secondary side DC terminal of the power conversion device to transmit active power output from the secondary side DC terminal to the primary side DC terminal to be a part of active power input to the primary side DC terminal.