To provide a high pressure self-cleaning and mixing device for manufacturing molding parts of a polyurethane material product containing a filler.

In a high pressure self-cleaning and mixing device for manufacturing a reinforced polyurethane mixture, a fluidized filling material is blended with a polyurethane mixture, and the device is provided at least with a mixing chamber for mixing first and second polyurethane components together, a discharge duct (In that case, a chamber is opened on the rear terminal of the discharge duct.), a narrow and long cleaning member movable reciprocatingly in the discharge duct and a feeding channel for feeding a fluidized filler material between the forward moving position for closing the mixing chamber and the backward moving position for opening the mixing chamber toward the discharge duct and extending in the vertical direction of a cleaning member. The feed channel is opened on a mixing area on the rear terminal of the discharge duct close to an outlet opening of the mixing chamber, and the polyurethane mixture is discharged from the mixing chamber into the discharge duct under the high turbulent flow condition.