Abstract: In a multi-chamber load-locking device which is placed between a loading station which places a wafer cassette which houses semiconductor wafers and a transfer chamber which conveys the semiconductor wafers and in which lock-loading device chamber space is divided into two by the vertical motion of a plate, a device which comprises: sealing means by which the chamber space is selectively divided into two by contacting the plate and a state of no airflow is caused; a cylindrical cam provided with the same axis as that of the chamber; and a rotary actuator dynamically connected with the cylindrical cam, wherein the turning moment of the rotary actuator is converted into the vertical thrust of the axis and the plate rises and descends.