A mist generator device comprising: a mist generation unit that generates mist from a liquid; a mist flow pipe connected to the mist generation unit, wherein the mist from the mist generation unit flows through the mist flow pipe; a tubular mist nozzle that releases the mist, which is supplied from the mist generation unit through the mist flow pipe, out of the mist generator device, and a high-voltage discharge device that performs a high-voltage discharge to ionize the mist, wherein the mist nozzle includes a mist entrance, a mist exit, and first and second inner constrictions (54, 55) located at an inner side of the mist nozzle, wherein each inner constriction (54, 55) includes a step (54a, 55a) that decreases an inner diameter of the mist nozzle from the mist entrance toward the mist exit, a first inner surface located closer to the mist entrance than the step of the first inner constriction and the step of the second inner constriction, and a second inner surface located closer to the mist exit than the step of the first inner constriction; wherein the mist releasing direction is inclined upward by a predetermined angle (α) from a reference plane that is parallel to the plane on which the mist generator device is set, the mist nozzle is located directly above the high-voltage discharge device and within the mist flow pipe; the step of the first inner constriction has a first height, the step of the second inner constriction has a second height, which is greater than the first height; the first inner surface extending from the first inner constriction to the mist entrance has a first axial length, the second inner surface extending from the second inner constriction to the first inner constriction has a second axial length, wherein L1>H1 and L2>H2; and the first inner surface is shorter in an axial direction of the mist nozzle than the second inner surface. a mist generation unit that generates mist from a liquid; a mist flow pipe connected to the mist generation unit, wherein the mist from the mist generation unit flows through the mist flow pipe; a tubular mist nozzle that releases the mist, which is supplied from the mist generation unit through the mist flow pipe, out of the mist generator device, and a high-voltage discharge device that performs a high-voltage discharge to ionize the mist, wherein the mist nozzle includes a mist entrance, a mist exit, and first and second inner constrictions (54, 55) located at an inner side of the mist nozzle, wherein each inner constriction (54, 55) includes a step (54a, 55a) that decreases an inner diameter of the mist nozzle from the mist entrance toward the mist exit, a first inner surface located closer to the mist entrance than the step of the first inner constriction and the step of the second inner constriction, and a second inner surface located closer to the mist exit than the step of the first inner constriction; wherein the mist releasing direction is inclined upward by a predetermined angle (α) from a reference plane that is parallel to the plane on which the mist generator device is set, the mist nozzle is located directly above the high-voltage discharge device and within the mist flow pipe; the step of the first inner constriction has a first height, the step of the second inner constriction has a second height, which is greater than the first height; the first inner surface extending from the first inner constriction to the mist entrance has a first axial length, the second inner surface extending from the second inner constriction to the first inner constriction has a second axial length, wherein L1>H1 and L2>H2; and the first inner surface is shorter in an axial direction of the mist nozzle than the second inner surface.