An optical measurement apparatus, comprising: an optical unit; and a tray extracted from a main body through an opening formed in a predetermined portion of the main body or retracted into the main body through the opening towards an optical unit provided in the main body, wherein a cartridge into which a sample is injected is seated onto the tray; a cartridge support fixing the cartridge at a position corresponding to the optical unit after the cartridge has been seated on the tray and the tray has been retracted into the main body; the optical unit applying light to the sample contained in the fixed cartridge and receiving light from the sample; and a control unit calculating a measurement value of the sample using the applied light and the received light; and wherein the tray has a seating depression into which the cartridge is seated, and further comprising a cartridge installation detection unit detecting whether the cartridge has been mounted on the tray when the tray is in the retracted state, and wherein the cartridge installation detection unit detects whether the cartridge has been mounted to the tray by detecting a difference between light reflected by the tray seating depression and light reflected by the cartridge; wherein the seating depression has a predetermined depth and has a shape corresponding to a peripheral shape of the cartridge; wherein the cartridge has a circular shape, with a sample injection hole formed in a central portion of one surface of the cartridge; and wherein the cartridge support comprises: pressing members slidably provided on opposite sides of the circular cartridge which has been disposed below the optical unit by the retraction of the tray; and elastic members supporting the corresponding pressing members and pressing the pressing members towards the cartridge. an optical unit; and a tray extracted from a main body through an opening formed in a predetermined portion of the main body or retracted into the main body through the opening towards an optical unit provided in the main body, wherein a cartridge into which a sample is injected is seated onto the tray; a cartridge support fixing the cartridge at a position corresponding to the optical unit after the cartridge has been seated on the tray and the tray has been retracted into the main body; the optical unit applying light to the sample contained in the fixed cartridge and receiving light from the sample; and a control unit calculating a measurement value of the sample using the applied light and the received light; and wherein the tray has a seating depression into which the cartridge is seated, and further comprising a cartridge installation detection unit detecting whether the cartridge has been mounted on the tray when the tray is in the retracted state, and wherein the cartridge installation detection unit detects whether the cartridge has been mounted to the tray by detecting a difference between light reflected by the tray seating depression and light reflected by the cartridge; wherein the seating depression has a predetermined depth and has a shape corresponding to a peripheral shape of the cartridge; wherein the cartridge has a circular shape, with a sample injection hole formed in a central portion of one surface of the cartridge; and wherein the cartridge support comprises: pressing members slidably provided on opposite sides of the circular cartridge which has been disposed below the optical unit by the retraction of the tray; and elastic members supporting the corresponding pressing members and pressing the pressing members towards the cartridge. pressing members slidably provided on opposite sides of the circular cartridge which has been disposed below the optical unit by the retraction of the tray; and elastic members supporting the corresponding pressing members and pressing the pressing members towards the cartridge.