A die for forming the honeycomb structure includes: a plate-like die main body including an introducing portion provided on the side of one surface thereof and having a plurality of back holes and a forming portion provided on the side of the other surface thereof and having slits; and a back plate detachably attached to the surface of the introducing portion and having a plurality of through holes connected to the back holes of the introducing portion. Through hole opening portions of the through holes formed in the back plate in the one surface of the die main body have such an enlarging shape as to enlarge toward the one surface of the die main body. The die for forming the honeycomb structure can decrease the resistance of a forming material during extrusion.