To provide a variable orifice device that enables easy and accurate flow regulation of a fluid flowing in pipes.

The variable orifice device has a fixed orifice 3 between flanges 1 and 2 on fluid pipes p1 and p2, and has adjacently a movable orifice 4 rotatable on the pipes. Each orifice 3, 4 has at least one or more bores 11, 12 in advance. By turning about the pipes of a rod tool 6 inserted in a hole 5 formed in a flange on the movable orifice 4, the shape or size of the bore passing through both orifices 3 and 4 can be changed.