An extrusion die for extruding a honeycomb structure having a thick outer peripheral wall without generating any distortion or deformation therein, comprises a die body provided with a plurality of disconnected feed passageways and interconnected grid-shaped extrusion slots, an annular die mask which is closely contacted with the outer peripheral portion of the outlet face of the die body. In the outlet face of the die body, along the inner peripheral wall of the die mask, an annular groove of which depth is smaller than that of the extrusion slots is formed so as to open in the extruding direction.