PURPOSE: To increase the reliability of optical measurement for specimens by providing an optical detection means inside an incubator to eliminate possible deterioration of cell, killing, and contamination by pasteurization.

CONSTITUTION: An incident optical fiber part 3 to introduce light from a light source 6 set on the outside of an incubator and an optical detection means 2 to introduce light passed through a container into an optical analyzing part set separately from the incubator are provided at a specified part of the incubator in which the stored container is moved around the inside of the incubator by a transport mechanism 4. The transport system is of a one rotation merry-go- round by belts, and plates 7 are fed properly to an optical detection mechanism 5 in the incubator by the action of the transport mechanism 4. The transported plates 7 are detected properly for their absorbancies by the action of the optical fiber 3.