Disclosed herein is a latch device for a movable anchor in a passive seat belt system for mounting on a vehicle. The latch device includes a movable anchor, a latch releasably engageable with the movable anchor, actuator means releasably holding the latch in engagement with the movable anchor, an actuator member for bringing the latch into engagement with the movable anchor by way of the actuator means when the movable anchor moves to its occupant-restraining position, and switch means associated with the latch in such a way that it is actuated when the movable anchor has reached the occupant-restraining position and the latch has been brought into engagement with the movable anchor. The position of the latch is directly related to whether the movable anchor has been locked by the latch or not. It is thus necessary to provide only one switch means for stopping the rearward movement of the movable anchor and for confirming the latching between the movable anchor and the latch. The latch device has been rendered compact and economical.