A pressure regulating valve for a cupping negative pressure apparatus is provided with an upper pressure regulating valve screw cap and a lower pressure regulating valve body having a metal nut structure inside, and the metal nut structure is provided with a plurality of nut pressure relief holes. The pressure regulating valve screw cap can be tightened to block circulation of the nut pressure relief holes. A muffler cover assembly seat is disposed on an outermost side of a metal nut structure assembly seat for assembling a muffler cover, small holes for circulating air are disposed between the muffler cover and the metal nut structure assembly seat. The pressure regulating valve body has negative pressure communication holes for sucking and discharging air and the negative pressure communication holes are communicated or plugged by quick-plug screw caps. A filter cotton is disposed in the pressure regulating valve body.
