A core conductor of a coaxial connector is electrically connected to a terminal electrode which is provided at an end of a surface of a board, and a shell GND of the coaxial connector is electrically connected to a GND electrode which is provided at an end of a back surface of the board in a relay connector. The shell GND has a substantially columnar outer shape. The relay connector includes: a conductive first block having a first surface and a second surface being opposite to the first surface, the first block formed with a through hole, the coaxial connector being provided in the through hole, a part of the shell GND being provided in the through hole, the core conductor of the coaxial connector being projected from the first surface of the first block; and a conductive second block provided with a board rest part on which the board is to be placed, the second block operable to relatively move with respect to the first block and being electrically connected to the first block.