A measurement method for brown adipose tissue includes a light input step of inputting near-infrared light from a light input unit into a measurement target portion, a light detection step of detecting light intensity of the near-infrared light having propagated through an interior of the measurement target portion by a light detection unit, and a calculation step of calculating an index value for a BAT amount from an oxygenated hemoglobin concentration or the like of the measurement target portion, which is acquired by near-infrared spectroscopy based on the detection result by the light detection unit.
