A connection unit for electrically connecting a DUT mounting board, on which an IC socket is mounted, with a testing apparatus for testing an electronic device inserted into the IC socket, the connection unit has a holding substrate provided to face the DUT mounting board and a connection-unit-side connector, which is provided on the holding substrate to be able to change a position of the connection-unit-side connector on the holding substrate, for being connected to a performance-board-side connector included in the DUT mounting board.