To provide a demolding device for a hydraulic inorganic molding without apprehension dropping down a molding from a sucker board during demolding even when partial improper suction is generated at suction time of the molding to the sucker board.

In a demolding device for a hydraulic inorganic molding used in the case of suction-demolding the press-molded hydraulic inorganic molding from a press mold by a sucker board, in a sucker surface 11 provided in a lower surface of the sucker board 1, a plurality of suction holes 12 are provided, in each suction hole 12, a suction valve 2 is provided, it is constituted by protrusively providing a valve lever 22 having an external diameter smaller than an internal diameter of the suction hole 12 under a closing plate 21, the valve lever 22 is inserted in each suction hole 12, the closing plate 21 is brought into close contact with a reverse surface of the sucker surface 11, the suction hole 12 is closed, and, when a lower end of the valve lever 22 is protruded downward from the sucker surface 11, the suction hole 12 is closed by the suction valve 2, and, when its closing plate 21 is floated from a reverse surface of the sucker surface 11, the suction hole 12 is opened.