To provide a microchip capable of accurately measuring absorbance by reducing the possibility of adverse effects on the light incident surface or the like of a detection part.

The microchip is equipped with a specimen inlet part comprising a plate member and introducing a specimen, the reagent reacting with the specimen, a mixing part for mixing the reagent and the specimen to form a measuring liquid and the detection part filled with the measuring liquid. The detection part has a recessed place, having a light incident surface or a light-emitting surface formed at least to one end part in the longitudinal direction.