Provided is a cerebral blood flow measurement method of quantitatively measuring cerebral blood flow, the measurement method including: a tracer introducing step of introducing a tracer into a blood vessel； a light applying step of applying measurement light including an absorption wavelength of the tracer to a head； a light detecting step of detecting the measurement light propagating in the head and generating a detection signal based on light intensity of the measurement light； and a calculation step of calculating cerebral blood flow on the basis of a relative change over time Δ；Q of a concentration of the tracer in a brain tissue which is acquired on the basis of the detection signal and a predetermined relationship between a change over time of a concentration Pa of the tracer in an artery of the head and cerebral blood flow.
