This extrusion-molding device is provided with: a housing having a channel for conveying a pasty starting material composition; screws for mixing the starting material composition and conveying the same downstream, the screws being provided upstream from the channel; a die from which a molded article formed from the starting material composition is extruded, the die being provided downstream from the channel; a resistance tube for connecting the channel and the die; a flow volume adjustment plate provided between the screws and the die, having a plurality of through-holes passing therethrough in the thickness direction thereof, and provided removably in relation to the housing; and an upstream-side blocking member for simultaneously blocking upstream-side openings of some of the plurality of through-holes when fitted to the flow volume adjustment plate, the blocking member being provided removably in relation to the upstream-side surface of the flow adjustment plate.