The “Improved hydraulic diaphragm valve, for fluid flow regulation” which constitutes the object of this Patent, contains a semi-conical deflector (2) with an open and flat upper face (3), its perimeter being an isosceles triangle and its cross section equal to that of the valve passage, the semi-cone (2) and the triangle (3) being oriented towards the intake of the fluid. The diaphragm (4) is seated on the flat section (3) pressed by the fluid contained in the chamber formed by the cover (5) and the diaphragm (4); whilst by draining the fluid from the chamber, the intake pressure lifts the diaphragm (4) off its seating. Shutting or reducing flow is produced in the upstream direction, and opening or increasing flow, downstream.