PURPOSE: An assay apparatus of an optical mode is provided to quickly and accurately measure and to improve reliability. CONSTITUTION: An assay apparatus of an optical mode comprises: a tray(20) which has a sample-injected cartridge; a cartridge fixing unit for fixing the cartridge on an optical unit; the optical unit which irradiates light to the sample and receives light from the sample; and a control unit which calculates sample value using irradiated light and received light of the optical unit. The apparatus further comprises a cartridge installation detection unit.
