An array device for biomolecule quantification includes a base having a plurality of wells, a cover having a gap between the base and the cover and laid over the base to cover openings of the plurality of wells, an injection port communicating with the gap between the base and the cover, and a discharge port formed at a position apart from the injection port and communicating with the gap between the base and the cover. In the device after an aqueous solution is filled in between the base and the cover, a liquid containing biomolecules is introduced from the injection port into the gap between the base and the cover to discharge surplus aqueous solution, the surplus aqueous solution being outside the plurality of wells, from the discharge port, and the biomolecules are transferred by diffusion to the aqueous solution filled in the plurality of wells.