An adhesion method capable of strongly adhering two members without using an adhesive and without impairing a fine structure or optical properties of a joining surface, and a biochemical chip and optical component made by the same are provided.The adhesion method includes step A of forming a coating film 13 of a first film compound having a first functional group on a first joining surface 11 of a first member 21, step B of forming a coating film 14 of a second film compound having a second functional group on a second joining surface 12 of a second member 22, and step C of bringing the first joining surface 11 into contact by pressure with the second joining surface 12 while bringing a coupling agent having at least one coupling reactive group that forms a bond by a coupling reaction with the first functional group and the second functional group into contact with the first and second functional groups to form bonds by the coupling reaction.