Provided is a biological-information measurement device having a small-sized device configuration without a reduction in measurement precision. Reflected light from a measurement object (10) is split using a rotary diffraction grating (110), and the space requirements and number of components of a light-splitting optical system can thereby be reduced. A reflecting member (140) for reflecting light incident from a measurement probe (106) instead of the measurement object (10) and emitting the light to the measurement probe (106) is also provided, whereby an optical path for obtaining a measurement signal and an optical path for obtaining a reference signal can be configured in common, space requirements can be reduced, and precision of calibration can be enhanced. As a result, particularly the light-splitting optical system and a reference signal optical system can be reduced in size without a reduction in measurement precision.
