PURPOSE: To make it possible to use two pallets alternatively in a space for only one pallet so as to replace a work, by providing a driving apparatus for rotating half a rotation of a pallet support table supported rotatably by a rotating shaft.

CONSTITUTION: The work replacing apparatus 1 has the pallet support table 7 equipped with a first shaft section 5 and a second shaft section 6 respectively supported rotatably by bearing apparatuses 3, 4 provided to a frame 2. A rotatively driving motor 11 is connected to the second shaft section 6 of the support table 7 and can rotatably drive intermittently the support table 7 by 180°. A pallet guide 8 of the support table 7 guides freely slidably the transport pallet 9, which is provided with a work 24. After the completion of the machining, a table 17 is moved so that the pallet 9 is connected with a pallet reciprocation driving apparatus, the apparatus 12 is actuated, the pallet 9 is transferred to a prescribed position of the support table 7, and the work is removed.