PROBLEM TO BE SOLVED: To provide an optical measurement system in which a blood flow change appearing in the time zone before and after the starting time of a task period can be observed in an interested area of a brain of an examinee.SOLUTION: An optical measurement system includes control units 21, 22 for obtaining S pieces of measurement data concerning time change of the brain activity of an examinee, by irradiating the examinee with light using N pieces of light sending probe 12 and detecting light with M pieces of light receiving probe 13. The optical measurement system includes selection means 24 for selecting Y pieces of light sending probe (where Y