A reaction plate includes a welded plastics planar laminate consisting of an aperture plate and a film, the aperture plate having at least one planar surface and a plurality of apertures in the planar surface of the apertured plate and the film being attached to the planar surface of the apertured plate around the or each aperture by welding. The welding is preferably laser or transmission welding. A method of forming such reaction plates using diode laser welding. An apparatus is provided for handling such reaction plates including performing polymerase chain reactions (PCRs) or primer extensions therewith.

A formed article obtained by performing laser welding on a transmitting resin member and an absorbing resin member, includes: a bonded part where the transmitting resin member and the absorbing resin member are bonded to each other by the laser welding, in which a molten pool is observed at the bonded part in a cross section that includes a normal to the transmitting resin member or the absorbing resin member and is orthogonal to a scanning direction of a laser beam, an area of the molten pool is 0.210 mm.sup.2 or more and 1.00 mm.sup.2 or less, the transmitting resin member and the absorbing resin member are each molded from a resin composition, the resin composition contains a thermoplastic resin, the thermoplastic resin contains at least a polyamide-based resin (A1), and a glass transition point temperature of the resin composition is 85 C. or higher.

An operation member is provided and includes a first resin member having a plate shape and formed of a material that transmits laser light; and a second resin member having a tubular shape and formed of a material that absorbs the laser light. The first resin member and the second resin member are laser-welded in an opening included in the second resin member. The second resin member includes a bonding projection provided to project from an inner circumferential surface of the opening toward an inner diameter side of the second resin member. An outer circumferential portion of the first resin member is placed over the bonding projection of the second resin member. The outer circumferential portion of the first resin member is laser-welded to the bonding projection of the second resin member.