In addition to irradiating examination light toward the inside of the bead of the subject and detecting the examination light reflected from the head: structural data indicating the head structure, wherein the head is divided into multiple materials and the various materials are further divided into multiple elements, are stored in a structural data storage unit set up in a specified region of memory; the optical properties of the aforementioned elements are calculated from a given specified initial value; the hemodynamics inside the brain of the subject are calculated based on the optical properties thereof, and the aforementioned initial values are taken to be the optical properties when the light intensity signal values, provisionally calculated from optical properties under the assumption that the optical properties are uniform for each of the aforementioned materials, are in a fixed range of the actually measured light intensity signal values.
Brain function measurement device, brain function measurement method, and brain function measurement program