To provide a method for joining fiber reinforced thermoplastic resins capable of improving joining strength, more particularly, the joining strength when a reinforced fiber contained in a joined surface is a continuous fiber or a discontinuous fiber having a number-average fiber length of 10 mm or longer.

In this method, when two kinds of fiber reinforced thermoplastic resins are joined, a thermoplastic resin material is arranged in advance on the joined surface of at least one of the fiber reinforced thermoplastic resin, and subsequently the two kinds of fiber reinforced thermoplastic resins are joined.