A die (1) for extrusion molding includes an extrusion port (1c) configured to extrude a plastic composition, and a plastic flow channel (111) configured to cause the supplied plastic composition to flow to the extrusion port. The plastic flow channel (111) includes a supply flow channel (111a), and an extrusion flow channel (111b). The supply flow channel (111a) is configured to be supplied with the plastic composition. The extrusion flow channel (111b) has an upstream end coupled to the supply flow channel, and downstream end having the extrusion port. In the extrusion flow channel, a flow channel cross-sectional area perpendicular to the flow direction of the plastic composition in the extrusion flow channel (111b) gradually changes to the extrusion port (1c), and an inner wall surface of a flow channel has a protruding surface protruding toward an inside of the flow channel in a cross section including an extrusion central axis (g) and parallel to the extrusion central axis (g).