A fluid pressure regulating apparatus comprises a body having a fluid passage to be connected to a machine driven by a pressurized fluid and to a pressurized fluid supplying source. The rotation of a ring member on the outer surface of the body, around the longitudinal center line thereof, responsively moves a regulating member inside the body, so as to vary selectively the pressing force, applied by the regulating member to an urging member sandwiched between the regulating member and an actuator member when the actuator member is moved from a first position to a second position inside the body by an increased urging force of the urging member, a valve body is driven by the actuator member and moved from a closed position to an open position. The valve body is maintained in its open position by the actuator member, to which the increased urging force is applied, against the pressure of the fluid in the passage. When the actuator member is in its first position (i.e., without an increased urging force being applied thereto), the valve body is allowed to move toward its open position. Thus, the urging force responsively arising from the rotation of the ring causes movement of the valve body, which movement thereby regulates the pressure of the fluid supplied to the machine.