In a biological optical measuring instrument, when displaying a biological
variation in a predetermined region of a subject through irradiating
light to the subject and processing light signals obtained by detecting
the transmitting light, the light signals of a plurality of sections
having a predetermined time interval are extracted, section data are
prepared from the respective extracted light signals, the plurality of
the prepared section data are added and averaged, prior to preparing
averaged section data for the predetermined time interval a light signal
section containing noise components is specified from differential values
of the extracted light signals and the section data of the light signal
containing the noise components is excluded from the averaging operation,
thereby, a biological optical measuring instrument is provided which
permits to remove the section data containing noise components are
automatically removed through computation without relying upon visual
observation, to obtain highly reliable measurement result quickly and to
display the same.