PURPOSE: To make it possible to form and close a molten metal passage with a simple mechanism and to manufacture of castings having high quality by applying the above device to bottom pouring casting by a rotary casting mold.

CONSTITUTION: The outlet blocking device for molten metal is formed with the molten metal passage for tapping to the casting mold by interposing the passage between the tap hole of a vessel for housing the molten metal and the inlet part of the casting mold connected to the vessel and blocks the molten metal passage in order to stop the tapping to the casting. This device comprises housings 41 and 43 and valve plates 11, 21 and 31 which are superposed on each other in the housings and are rotatably mounted. Eccentric through-holes are respectively formed in the valve plates and the formation or blockage of the molten metal passage is executed by rotating the valve plates to put these through-holes 15, 25 and 25 into a superposed state or non-superposed state.