PURPOSE: To increase the weldability of a needle seat in regard to a frame seat and provide an excellent water stopping quality by forming a needle seat outer periphery edge portion at a hollow jet valve used for dam water discharge facilities out of a plate body projecting in a flange shape from a needle peripheral edge portion.

CONSTITUTION: At a hollow jet valve, a needle 3 fixed at the tip of a plunger 4 is arranged in opposition to an upstream part opening 2 inside a frame 1, and the plunger 4 is made movable forward/backward toward the opening 2 by means of a drive mechanism 6. In this instance, a needle seat 11 whose purpose is to conduct water stopping between the frame 1 and the needle 3 by butting against a frame seat provided at a frame 1 inner periphery surface, is provided at the peripheral edge portion of the needle 3. At this needle seat 11, its outer periphery edge portion is formed out of a plate body projecting in a flange shape from the peripheral edge portion of the needle 3, and fixation at the needle 3 is made by means of a fixation bolt 12. As result, the peripheral edge portion of the needle seat 11 is made to follow softly a bad condition under which the needle 3 is put in the opening, and an excellent water stopping quality is secured.