A cuvette capable of suppressing the complication of the structure of each part of an analyzer and enabling the stirring of a specimen in a short time. The cuvette comprises a first body part positioned on a bottom part side, having inner and outer surfaces of circular shape in horizontal cross section, and receiving a measuring beam and a second body part positioned on an opening side, having an inner surface of non-circular shape in horizontal cross section and an outer surface of circular shape in horizontal cross section.
