PURPOSE: To actuate a stopper and a lock piece by providing an actuating device on either of them.

CONSTITUTION: When it comes to be in the state where an elevating rail 9 is connected to an upper side guide rail 6, a travelling car travelling on the upper side rail 6 moves to get on the elevating rail 9 and stops. In this state, the upper side rail 6 and the elevating rail 6 are locked by a lock piece 23, and a stopper 30 is retreated from a passage of the travelling car. When the travelling car is placed on the elevating rail 9, the lock piece 23 comes to be in the unlocked state, interlocked with it, the stopper 30 is projected on the passage of the travelling car to prevent derailing of a following travelling car from the upper side guide rail 6.