To stably retain a measurement chip at a specific position, without deviation in a sensor utilizing total reflection attenuation.

The measurement chip 10 is composed by forming a dielectric block 11, having a surface 11a where a metal film 12, is formed, and a light incidence end face 11b and an emission end face 11c of a light beam and a sample retention section 13 for retaining a sample on the metal film 12 in one piece. A measurement chip retention hole 21 and a leaf spring 23 at two sides adjacent to the retention hole 21 are provided on a turntable. The measurement chip 10 is inserted into the retention hole 21, and the measurement chip 10 is energized to a corner C of the retention hole 21 by the leaf spring 23 for retention.