A board insertion device includes a holder; and an insertion guider which is slidably provided in the holder in an insertion direction of the board into the connector and includes a distal end portion protruding in the insertion direction from a first end surface of the board held in the holder and abutting against the connector during insertion of the board into the connector. Furthermore, the board insertion device includes an abutting portion; and a conversion mechanism converting a change of a relative position between the holder and the insertion guider into a movement of the abutting portion for changing a position of the ejector from a closed position to an open position. in which the conversion mechanism is provided in the insertion guider and engaged with the holder or is provided in the holder and engaged with the insertion guider.