A biological material measuring instrument is described. The biological material measuring instrument includes a rotating body and a main body. The rotating body includes one or more cartridge holders having cuvettes in which a reagent and an analyte in a sample react. The main body includes a pair of light-emitting parts and light-receiving parts to optically measure the analyte in the sample. The rotating body further includes a light-emitting optical waveguide for guiding the light of the light-emitting parts to the cuvette, and a light-receiving optical waveguide for guiding.