A vacuum regulating valve is capable of precisely controlling the flow of a fluid so that the flow rate may increase gradually in an initial stage of a valve opening operation. The vacuum regulating valve includes a valve casing having a valve chamber and provided with a first opening connected to a vacuum vessel and a second opening connected to a vacuum pump, a valve seat, a valve element seated on the valve seat, a valve stem connected to the valve element, a bellows sealing the valve stem therein, and a baffle member attached to the back surface of the valve element and surrounding the bellows. The baffle member is formed in an axial length such that the baffle member is able to cover the second opening entirely when the valve element is seated on the valve seat. The outside diameter of the baffle member is determined such that an outside space of the smallest possible thickness is defined between the outer circumference of the baffle member and the inner circumference of the side wall of the valve casing, and the thickness of the outside space is great enough to keep the baffle member spaced from the inner circumference of the side wall of the valve casing and is small enough to prevent a fluid from flowing through the outside space into an inside space formed between the baffle member and an imaginary cylinder circumscribed about the bellows.