Provided herein is a device for quantitative analysis of a micro-volume solution. The device comprises a base portion provided with a light-emitting fiber, a movable arm provided with a light-receiving fiber, and at least one positioning block disposed between the movable arm and the base portion so that an optical path with a constant length is formed between the light-emitting fiber and the light-receiving fiber when the positioning block is clamped by the movable arm and the base portion. The solution concentration related to the absorbance with respect to the standard optical path length may be evaluated based on the built-in database and the optical intensity of light having passed through the solution as detected by a light sensor.