To provide a resin laminated sheet including an inner rib.

A method for manufacturing the resin laminated sheet includes: a step for positioning thermoplastic resin sheets P1, P2 between a pair of molds provided with a slide core 300; a step for forming a sealed space between the thermoplastic resin sheet P1 and a cavity of one mold; a step for enlarging the size of the thermoplastic resin sheet P1 by projecting the slide core 300 toward the other mold while sucking the sealed space as well as for projecting a part of the sheet toward the other mold in a U-shaped manner; a step for welding the thermoplastic resin sheet to the other thermoplastic resin sheet; a step for forming a sealed part 280 inside the two thermoplastic resin sheets by welding peripheries of the thermoplastic resin sheets; a step for making inner surfaces of the thermoplastic resin sheets projected in a U-shaped manner face to each other by withdrawing the slide core 300; and a step for forming the inner rib by welding the facing inner surfaces.