A state of attenuation in total internal reflection is detected by the use
of a measuring apparatus having a measuring unit and a reference unit and
a measuring system which corrects result of detection by the measuring
unit on the basis of result of detection by the reference unit and
measures the change of a state of attenuation in total internal
reflection on the basis of the corrected result of detection by the
measuring unit. The difference in sensitivity between the measuring unit
and the reference unit is detected before initiating the measurement of
the change of a state of attenuation in total internal reflection, and
result of measurement by the measuring system is calibrated on the basis
of the difference in sensitivity between the measuring unit and the
reference unit.