PROBLEM TO BE SOLVED: To compensate acoustic mode dependency of concentration measurement sensitivity to a measurement target constituent included in a measurement target object.SOLUTION: Two of laser diodes 1-1 to 1-3 emit light with two waves different in wavelength while modulating intensity of the light by signals with the same frequency and also a different phase. An acoustic sensor 6 detects photoacoustic signals generated from a measurement target object 11. An information processing device 10 estimates acoustic modes with respect to two time points different in wavelength of light changing the intensity or two time points different in temperature of the measurement target object 11 respectively on the basis of a change amount of optical intensity acquired from a result of measurement of the optical intensity when intensity of the measured signal gets lowest and a change amount of optical intensity acquired from a data set, and determines a correction coefficient of concentration measurement sensitivity to a measurement target constituent on the basis of the estimated acoustic mode and the known relationship between the concentration measurement sensitivity to the measurement target constituent included in the measurement target object 11 and the acoustic mode.SELECTED DRAWING: Figure 3
