PURPOSE: To prevent the lateral oscillation of a transfer device effectively by forming oscillation preventing mechanism of an engaging piece provided on one side and a positioning guide member provided on the other side, and providing the positioning guide member with a groove piercing long in the advancing direction of travelling trucks so as to be engaged with the engaging piece.

CONSTITUTION: In a device supporting a cage like transfer device 4 pendently at travelling trucks 3, 3 supported, in the freely travelling state, at a monorail 1 supported at a ceiling or the like, a positioning guide member 7 long in the advancing direction of the travelling trucks 3, 3 is laid on the floor, in the stop position of the transfer device 4. This positioning guide member 7 is pierced with a groove 7a provided long in the advancing direction of the travelling trucks 3 so as to be engaged with a plate like engaging piece 8 provided protrusively on one lower end side of the transfer device 4, and oscillation preventing mechanism is formed of this engaging piece 8 and the positioning guide member 7. Accordingly, when the transfer device 4 stops in the transfer position of parts, the engaging piece 8 is engaged with the groove 7a of the positioning guide member 7 to prevent the oscillation of the transfer device 4.