To facilitate a connection of air passages by making it hard to release the connection between a body unit and a cuff unit. An engagement hook 18 of a cuff unit M2 and an engagement hole 58 of a body unit M1 are engaged with each other by making the body unit move in a direction orthogonal to a connecting surface and subsequently slide in a direction A parallel to the connecting surface, and simultaneously air passage connection holes 31a and 40a of both units are connected, and further a lock claw 19 is provided in the cuff unit, to inhibit the movement of the body unit in a direction B opposite to the direction A, in an engagement state.
