The present invention provides a pattern forming method which makes the roughness of a pattern without generating pattern collapse, increases pattern mask selectivity, and forms a fine pattern without using a guide pattern. A pattern forming method according to one embodiment of the present invention includes a process of forming a pattern material layer which has an exposure part and a non-exposure part which become a porous material and are used as an etch object layer in an exposure process, on a substrate, a process of pattern-exposing a paten forming material layer and making the exposure part porous, a process of selectively dipping a filling material in the air gap of the exposure part and reinforcing the exposure part, and a process of removing the non-exposure part of the pattern forming material layer by dry etching and forming a preset pattern. [Reference numerals] (AA) Form a DSA material film on a semiconductor wafer; (BB) Pattern and expose the DSA material film; (CC) Selectively infiltrate a filling material on at least a surface of a void formed on an exposure part; (DD) Form a predetermined pattern by removing a non-exposure part by dry etching; (EE) Process 1; (FF) Process 2; (GG) Process 3; (HH) Process 4