Patent ID: 8268112

Claim:
A resin member joining method for joining two resin members which are configured to be irradiated with light for optical detection, comprising the steps of: mounting a first resin member having an optical transparency for an incident laser beam on a base board having a supporting surface being an optical mirror surface in such a way that a 1 - 1 surface of the first resin member is brought in contact with the supporting surface of the base board; coating a light absorbing agent capable of absorbing an incident laser beam on a 1 - 2 surface of the first resin member opposite to the 1 - 1 surface; superposing a 2 - 1 surface of a second resin member having an optical transparency for an incident laser beam onto the 1 - 2 surface of the first resin member across the coated light absorbing agent; and irradiating a laser beam to the coated light absorbing agent from a 2 - 2 surface side of the second resin member opposite to the 2 - 1 surface so as to melt the 1 - 2 surface of the first resin member and the 2 - 1 surface of the second resin member which are in contact with the coated light absorbing agent irradiated with the laser beam so that the first resin member and the second resin member are joined to each other, wherein the optical mirror surface is a surface having a surface roughness Ra in a range of 5 nm or more and 100 nm or less such that the laser beam is prevented from scattering on the supporting surface and heat generation caused by a scattered laser beam is prevented.