An optical measurement instrument for a living body having an optical fiber removed, which is composed so as to transmit a driving signal for the light source to a plurality of an irradiation parts (1011), as well as to convert a transmitted and received signal, between a processing and control unit (102) and the probe unit (101), to a row of serial digital signals, by having one driving device for light source (1014) and one multiplexer (1015), inside the probe unit (101).
