A fine particle measurement device comprising: a light illumination unit configured to emit light onto a fine particle flowing through a channel; a light detection unit configured to detect light generated from the fine particle; a position detection unit configured to obtain position information about the fine particle in the X and Z Cartesian axis directions, wherein the X axis direction is the emission direction of light onto the fine particle, the Z axis direction is perpendicular to the X axis direction and the Y axis direction is the flow direction of the fine particle, the position detection unit comprising: a first spectral device configured to separate scattered light generated from the fine particle into an S polarization component and a P polarization component, an S polarization detection device configured to receive light of the S polarization component, and an astigmatism device provided between the first spectral device and the S polarization detection device to give astigmatism to the S polarization component, wherein a light reception surface of the S polarization detection device is divided into four areas, which are an area A, an area B, an area C, and an area D, in a lattice manner, wherein the area A is not adjacent to the area C and wherein the position information about the fine particle in the Z axis direction is obtained from a difference Δ1, A - C, of detection values in the area A and the area C; and an arithmetic computation unit configured to correct, on the basis of the position information, intensity information about light generated from the fine particle obtained by the light detection unit. a light illumination unit configured to emit light onto a fine particle flowing through a channel; a light detection unit configured to detect light generated from the fine particle; a position detection unit configured to obtain position information about the fine particle in the X and Z Cartesian axis directions, wherein the X axis direction is the emission direction of light onto the fine particle, the Z axis direction is perpendicular to the X axis direction and the Y axis direction is the flow direction of the fine particle, the position detection unit comprising: a first spectral device configured to separate scattered light generated from the fine particle into an S polarization component and a P polarization component, an S polarization detection device configured to receive light of the S polarization component, and an astigmatism device provided between the first spectral device and the S polarization detection device to give astigmatism to the S polarization component, wherein a light reception surface of the S polarization detection device is divided into four areas, which are an area A, an area B, an area C, and an area D, in a lattice manner, wherein the area A is not adjacent to the area C and wherein the position information about the fine particle in the Z axis direction is obtained from a difference Δ1, A - C, of detection values in the area A and the area C; and a first spectral device configured to separate scattered light generated from the fine particle into an S polarization component and a P polarization component, an S polarization detection device configured to receive light of the S polarization component, and an astigmatism device provided between the first spectral device and the S polarization detection device to give astigmatism to the S polarization component, wherein a light reception surface of the S polarization detection device is divided into four areas, which are an area A, an area B, an area C, and an area D, in a lattice manner, wherein the area A is not adjacent to the area C and wherein the position information about the fine particle in the Z axis direction is obtained from a difference Δ1, A - C, of detection values in the area A and the area C; and an arithmetic computation unit configured to correct, on the basis of the position information, intensity information about light generated from the fine particle obtained by the light detection unit.