To provide the manufacturing method and the manufacturing device for the decorated extrusion formed part whose manufacturing device is simple and having a clear decorated part.

In the manufacturing method for a decorated gasket as the decorated extrusion formed part consisting of a main body part 10 for clogging a joint and the decorated part 2 consisting of projecting and recessing patterns provided on the main body part 10, by using a forming roll 3 with pattern recessed parts 31 for forming the decorated part on its outer peripheral surface 32, and by extruding a material 200 to be decorated from an extrusion die 41 for decorating to the forming roll 3, the decorated part 2 is formed by the pattern recessed parts 31. On the other hand, the main body part 10 is formed by extruding a main body part material 100 from an extrusion die 42 for the main body. Next, while rotating the forming roll 3, by pushing the outer peripheral surface of the forming roll 3 against the main body part 10, the decorated part 2 is joined to the surface of the main body part.