A method for bonding resin members by laser welding in which melting of a resin member can be prevented on the contact surface with a base or a tool used for bonding. In the bonding method, a resin member (1) is mounted on a base (3) and a surface of the base (3) in contact with the resin member (1) is an optical mirror surface. A surface of the resin member (1) is coated with a light absorbing agent (4), a resin member (2) is placed thereon and then a laser light (10) is irradiated from the resin member (2) side in order to melt the resin on the bonding surface of the resin member (1) and the resin member (2), thereby bonding the resin members together. The laser light (11) penetrated through the bonding surface reaches the contact surface where the resin member (1) and the base (3) are in contact with each other, and since the laser light (11) penetrates the bonding surface without being scattered or absorbed, melting of the resin member can be prevented.