There is disclosed a die 1 for forming a honeycomb structure comprises: a plate-like die substrate 2 having at least two surfaces 8, 9, in which back holes 3 for introducing a green material are formed in one surface 8, and slits 4 communicating with back holes 3 are formed in the other surface 9; an underlayer 5 disposed on the substrate 2 so as to coat at least a part of a portion constituting the back hole 3 and the slit 4; an intermediate layer 6 disposed so as to coat at least a part of the underlayer 5 and constituted of tungsten carbide particles whose average particle diameter is 5 .mu.m or less and containing W.sub.3C as a main component; and a surface layer 7 disposed so as to coat at least a part of the intermediate layer 6 and constituted of diamond and/or diamond-like carbon.