A reaction container includes a transparent base including a resin material and having recessed portions formed in one or more regions of the transparent base such that the recessed portions are recessed from a surface of the transparent base, and a cover member including a thermoplastic resin material and positioned on the transparent base such that the cover member forms a flow path including a gap extending over the recessed portions between the cover member and the surface of the transparent base and has a spacer portion welded by laser irradiation to the transparent base outside the one or more regions of the transparent base. The cover member absorbs infrared light and transmits light having a wavelength within a range of visible light such that the cover member has light transmittance in the range of from 480 nm to 570 nm.