A blood component concentration measurement device comprising: a four-wavelength light emitter (11, 12, 13, 14) configured to emit four kinds of wavelengths of light toward a predetermined site on a living body; a light receiver configured to receive the four kinds of wavelengths of light transmitted through the predetermined site on the living body; a received light intensity information acquirer configured to acquire received light intensity information for the four wavelengths on the basis of an optical signal received by the light receiver; an absorbance time change value acquirer configured to find time change values of absorbances corresponding to the four wavelengths on the basis of the received light intensity information of the four wavelengths; a calibration data table configured to store calibration data for finding a predetermined component in blood based on the absorbance time change values; and a component concentration acquirer configured to find the concentration of the predetermined component in the blood based on the absorbance time change values acquired by the absorbance time change value acquirer using the calibration data of the calibration data table; characterized in that an absorption wavelength for a blood component that is to be measured, an absorption wavelength for a blood component affecting the component to be measured, an absorption wavelength for water, and a wavelength that is not affected by the component to be measured, the blood component, the water, and other biological components are selected as the four wavelengths of the four-wavelength light emitter (11, 12, 13, 14). a four-wavelength light emitter (11, 12, 13, 14) configured to emit four kinds of wavelengths of light toward a predetermined site on a living body; a light receiver configured to receive the four kinds of wavelengths of light transmitted through the predetermined site on the living body; a received light intensity information acquirer configured to acquire received light intensity information for the four wavelengths on the basis of an optical signal received by the light receiver; an absorbance time change value acquirer configured to find time change values of absorbances corresponding to the four wavelengths on the basis of the received light intensity information of the four wavelengths; a calibration data table configured to store calibration data for finding a predetermined component in blood based on the absorbance time change values; and a component concentration acquirer configured to find the concentration of the predetermined component in the blood based on the absorbance time change values acquired by the absorbance time change value acquirer using the calibration data of the calibration data table; characterized in that an absorption wavelength for a blood component that is to be measured, an absorption wavelength for a blood component affecting the component to be measured, an absorption wavelength for water, and a wavelength that is not affected by the component to be measured, the blood component, the water, and other biological components are selected as the four wavelengths of the four-wavelength light emitter (11, 12, 13, 14).