PURPOSE: To aim at miniaturization in mechanisms at both sides of a machine tool and a stocker, by transmitting driving force out of a driving source of a pallet transfer mechanism installed in a traveling truck to both transfer mechanism for the machine tool and the pallet stocker, by means of coupling connection.

CONSTITUTION: On the basis of a pallet change command signal, a traveling truck 100 runs on traveling rails, while a truck 100a stops at a pallet changeable position at an interval with a pallet stocker 300b. Successively, a coupling 110 advances to the side of the stocker 300b from a side end of the truck 100a, and a taper part 111 is inserted into a taper hole of the coupling of the stocker 300b, then further a key member of the coupling is inserted into the inside of upper and lower notched parts of a member 112 and engaged thereat. Next, a pallet 400b is shifted by rolling motion of a backside roller on guide rails 301 and 103, and when being completely transferred onto the truck 100a, the coupling 110 is made to retract to the side of the truck 100 whrereby engagement is released, thus miniaturization in a pallet tranfer mechanism is made attainable.