A measurement device, comprising: a capturing part configured to cause a liquid to capture detection target particles contained in a gas and configured to cause a fluorescent substance, which is specifically bondable to the detection target particles, to be bonded to the detection target particles existing in the liquid; a droplet forming part configured to form aerosol-like droplets from the liquid supplied from the capturing part; and a measurement part (15, 15') configured to irradiate light onto the aerosol-like droplets and configured to measure a fluorescence intensity of the aerosol-like droplets, characterised in that the capturing part includes a cyclone provided with a gas introduction part, a liquid introduction part, a cyclone body, a suction-exhaust part configured to suction-exhaust and depressurize an interior of the cyclone body and configured to introduce a gas from the gas introduction part under a differential pressure so as to swirl the gas in a circumferential direction and a level detection part configured to detect a level of the liquid introduced into the cyclone body, wherein a wall surface of the cyclone body has a frusto-conical shape, wherein the wall surface of the cyclone body has a small-diameter-side end portion and a large-diameter-side end portion, the small-diameter-side end portion being positioned lower than the large-diameter-side end portion, wherein the gas introduction part is installed in the large-diameter-side end portion, and wherein the suction-exhaust part is installed in the large-diameter-side end portion, wherein the cyclone is configured to move the gas introduced from the gas introduction part downward while swirling it in the circumferential direction of the cyclone body, separate the detection target particles existing in the gas toward a wall surface of the cyclone body under a centrifugal force, introduce the liquid from the liquid introduction part, cause the liquid to capture the detection target particles separated toward the wall surface of the cyclone body, continuously supply the liquid to the droplet forming part, and adjust a flow rate of the liquid introduced from the liquid introduction part based on a detection result of the level detection part. a capturing part configured to cause a liquid to capture detection target particles contained in a gas and configured to cause a fluorescent substance, which is specifically bondable to the detection target particles, to be bonded to the detection target particles existing in the liquid; a droplet forming part configured to form aerosol-like droplets from the liquid supplied from the capturing part; and a measurement part (15, 15') configured to irradiate light onto the aerosol-like droplets and configured to measure a fluorescence intensity of the aerosol-like droplets, characterised in that the capturing part includes a cyclone provided with a gas introduction part, a liquid introduction part, a cyclone body, a suction-exhaust part configured to suction-exhaust and depressurize an interior of the cyclone body and configured to introduce a gas from the gas introduction part under a differential pressure so as to swirl the gas in a circumferential direction and a level detection part configured to detect a level of the liquid introduced into the cyclone body, wherein a wall surface of the cyclone body has a frusto-conical shape, wherein the wall surface of the cyclone body has a small-diameter-side end portion and a large-diameter-side end portion, the small-diameter-side end portion being positioned lower than the large-diameter-side end portion, wherein the gas introduction part is installed in the large-diameter-side end portion, and wherein the suction-exhaust part is installed in the large-diameter-side end portion, wherein the cyclone is configured to move the gas introduced from the gas introduction part downward while swirling it in the circumferential direction of the cyclone body, separate the detection target particles existing in the gas toward a wall surface of the cyclone body under a centrifugal force, introduce the liquid from the liquid introduction part, cause the liquid to capture the detection target particles separated toward the wall surface of the cyclone body, continuously supply the liquid to the droplet forming part, and adjust a flow rate of the liquid introduced from the liquid introduction part based on a detection result of the level detection part.