To provide a technique by which an —OH group can be effectively formed on a material surface for the purpose of making the material suitable for bonding (for example, for molecular bonding) that utilizes a chemical reaction (chemical binding). [Solution] A bonding method for bonding a substrate A and a substrate B, which comprises: a step for applying an agent that contains the compound (α) described below on the surface of the substrate A; a step for arranging the substrate B so as to face the compound (α) that is present on the surface of the substrate A; and a step for integrally bonding the substrate A and the substrate B by applying a force onto the substrate A and/or the substrate B. The compound (α) is a compound that has an OH group or an OH-forming group, an azide group and a triazine ring in each molecule, and the substrate A is configured using a polymer.