A pump device for supplying a working fluid to a drive actuator for driving a drive subject through a control valve, comprising: a variable capacity first pump configured to supply the working fluid to the drive actuator, the first pump having a discharge capacity that varies in accordance with a tilt angle of a swash plate; a tilt actuator configured to control the tilt angle of the swash plate of the first pump in accordance with a control pressure supplied thereto; a regulator configured to regulate the control pressure in accordance with a front-rear differential pressure of the control valve; a fixed capacity second pump configured to be driven by an identical drive source to that of the first pump; a resistor provided in a pump passage through which the working fluid discharged from the second pump is led; a control actuator configured to operate in accordance with a front-rear differential pressure of the resistor so as to drive the regulator to reduce the control pressure in response to an increase in the front-rear differential pressure of the resistor; an auxiliary passage configured to lead an auxiliary pressure to the control actuator, the auxiliary pressure acting on the control actuator against either an upstream side pressure or a downstream side pressure of the resistor; and a switch valve configured to switch between a state in which the auxiliary pressure is supplied to the control actuator through the auxiliary passage and a state in which the auxiliary pressure is shut off, wherein the control actuator comprises: a cylinder; a piston configured to move so as to slide freely through an interior of the cylinder; and a rod coupled to the piston and linked to the regulator, and a first pressure chamber into which the upstream side pressure of the resistor is led and a second pressure chamber into which the downstream side pressure of the resistor is led are provided in the interior of the cylinder, characterized in that a third pressure chamber into which the auxiliary pressure is led from the auxiliary passage is provided in the interior of the cylinder. a variable capacity first pump configured to supply the working fluid to the drive actuator, the first pump having a discharge capacity that varies in accordance with a tilt angle of a swash plate; a tilt actuator configured to control the tilt angle of the swash plate of the first pump in accordance with a control pressure supplied thereto; a regulator configured to regulate the control pressure in accordance with a front-rear differential pressure of the control valve; a fixed capacity second pump configured to be driven by an identical drive source to that of the first pump; a resistor provided in a pump passage through which the working fluid discharged from the second pump is led; a control actuator configured to operate in accordance with a front-rear differential pressure of the resistor so as to drive the regulator to reduce the control pressure in response to an increase in the front-rear differential pressure of the resistor; an auxiliary passage configured to lead an auxiliary pressure to the control actuator, the auxiliary pressure acting on the control actuator against either an upstream side pressure or a downstream side pressure of the resistor; and a switch valve configured to switch between a state in which the auxiliary pressure is supplied to the control actuator through the auxiliary passage and a state in which the auxiliary pressure is shut off, wherein the control actuator comprises: a cylinder; a piston configured to move so as to slide freely through an interior of the cylinder; and a rod coupled to the piston and linked to the regulator, and a first pressure chamber into which the upstream side pressure of the resistor is led and a second pressure chamber into which the downstream side pressure of the resistor is led are provided in the interior of the cylinder, characterized in that a third pressure chamber into which the auxiliary pressure is led from the auxiliary passage is provided in the interior of the cylinder. a cylinder; a piston configured to move so as to slide freely through an interior of the cylinder; and a rod coupled to the piston and linked to the regulator, and a first pressure chamber into which the upstream side pressure of the resistor is led and a second pressure chamber into which the downstream side pressure of the resistor is led are provided in the interior of the cylinder, characterized in that a third pressure chamber into which the auxiliary pressure is led from the auxiliary passage is provided in the interior of the cylinder.