Measuring apparatus comprises a rotating plate 17, a torque detection plate 18 disposed on a same axis parallel to the plate 17 with a given gap, a torque sensor about the plate 18 through the specimen held between two plates. The plate 18 is a total reflection prism which is made from a material that has a greater refractive index than the specimen and transmits UV and infrared light. An ultraviolet beam is directed onto the specimen through the prism. An infrared beam is directed into the prism. The infrared beam emerging from the prism after total reflection from the interface between the prism and the specimen is detected. A signal processor analyzes the infrared absorption spectrum of the specimen on the basis of the infrared beam. While the viscosity of the specimen in the curing process is measured, the signal processor simultaneously measures the infrared absorption spectrum.