A measurement device comprising: a vertically arranged light absorption cell comprising a hollow capillary tube with both open ends, the capillary tube to be filled with a sample; a light absorption cell mounting block attached on one end of the light absorption cell and comprising a light irradiation part positioned on top of the light absorption cell to irradiate light to one end of the light absorption cell, wherein the light absorption cell is arranged such that the light emitted from the light irradiation part flows through one end of the light absorption cell, passes through the capillary tube in the longitudinal direction of the light absorption cell, and is emitted from the other end of the light absorption cell; and a light receiving block comprising a dipping part for measuring light to immerse the other end of the light absorption cell in the sample and to detect light emitted from the other end of the light absorption cell, characterized in that the light absorption cell mounting block further comprises an upper frame and a lower frame and additionally comprises a spacer positioned between the upper frame and the lower frame and comprising a flow path to reduce or increase a pressure inside of the light absorption cell and an attachment surface connected to one end of the light absorption cell; and a pressure control part connected to the flow path of the spacer to increase or reduce the pressure inside of the flow path, wherein the light irradiation part comprises an optical fiber irradiating light, the upper frame additionally comprises an optical fiber connector to fix the optical fiber and a transparent blocking plate disposed between one end of the light absorption cell and the light irradiation part, and the lower frame additionally comprises a light absorption cell fixing part to fix the light absorption cell, wherein the flow path of the spacer can let the sample and a washing solution in and out of the light absorption cell by pressurizing or depressurizing. a vertically arranged light absorption cell comprising a hollow capillary tube with both open ends, the capillary tube to be filled with a sample; a light absorption cell mounting block attached on one end of the light absorption cell and comprising a light irradiation part positioned on top of the light absorption cell to irradiate light to one end of the light absorption cell, wherein the light absorption cell is arranged such that the light emitted from the light irradiation part flows through one end of the light absorption cell, passes through the capillary tube in the longitudinal direction of the light absorption cell, and is emitted from the other end of the light absorption cell; and a light receiving block comprising a dipping part for measuring light to immerse the other end of the light absorption cell in the sample and to detect light emitted from the other end of the light absorption cell, characterized in that the light absorption cell mounting block further comprises an upper frame and a lower frame and additionally comprises a spacer positioned between the upper frame and the lower frame and comprising a flow path to reduce or increase a pressure inside of the light absorption cell and an attachment surface connected to one end of the light absorption cell; and a pressure control part connected to the flow path of the spacer to increase or reduce the pressure inside of the flow path, wherein the light irradiation part comprises an optical fiber irradiating light, the upper frame additionally comprises an optical fiber connector to fix the optical fiber and a transparent blocking plate disposed between one end of the light absorption cell and the light irradiation part, and the lower frame additionally comprises a light absorption cell fixing part to fix the light absorption cell, wherein the flow path of the spacer can let the sample and a washing solution in and out of the light absorption cell by pressurizing or depressurizing.