An analyzer in which optical measurement is performed with respect to a sample placed in optically transparent cells of an analysis tool includes a light source unit, a light-receiving unit, a tray on which the tool is placed, and a drive mechanism for driving the tray. The tray includes a holding section that holds the tool in a predetermined position. The drive mechanism reciprocates the tray between a first position where the tool placed on the tray is exposed to the outside of the analyzer and a second position where the tool is accommodated inside the analyzer. The light source unit is disposed so that emitted light is incident on a cell of the tool when the tray is located in the second position. The light-receiving unit is disposed so as to receive light transmitted through the cell when the tray is located in the second position.