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 located at an inner side of the mist nozzle , wherein each inner constriction includes a step 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 (Z0) 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 (H1), the step of the second inner constriction has a second height (H2), which is greater than the first height (H1); the first inner surface extending from the first inner constriction to the mist entrance has a first axial length (L1), the second inner surface extending from the second inner constriction to the first inner constriction has a second axial length (L2), 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 located at an inner side of the mist nozzle , wherein each inner constriction includes a step 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 (Z0) 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 (H1), the step of the second inner constriction has a second height (H2), which is greater than the first height (H1); the first inner surface extending from the first inner constriction to the mist entrance has a first axial length (L1), the second inner surface extending from the second inner constriction to the first inner constriction has a second axial length (L2), 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 . <EOS>