The present invention intends to enable light path length to be kept the same between sample measurement and reference measurement and thereby improve measurement accuracy, and is an optical analyzer that analyzes a sample flowing through a pipe having translucency. In addition, the optical analyzer includes: a light source unit that has a light source and a condenser lens; a light detection unit that detects light of the light source unit; and a support mechanism that movably supports the light source unit and the light detection unit. Further, the support mechanism moves the light source unit and the light detection unit between a sample measurement position and a reference measurement position.