An optical measurement device is provided. The device includes first and second optical fibers; first and second reaction vessels, and a light guide stage coupled to the first and second optical fibers. The light guide stage is driven to simultaneously optically connect the first and second optical fibers with the first and second reaction vessels. The device includes a measurement device for receiving emissions from the first and second reaction vessels, and a connecting end arranging body that supports the first and second optical fibers along a path. The arranging body is driven along the path between a first position, in which the first optical fiber is optically connected with the measurement device so that light is transmittable from the first reaction vessel, and a second position, in which the second optical fiber is optically connected with the measurement device so that light is transmittable from the second reaction vessel.