A main object of the present disclosure is to provide a method for producing an active material wherein a volume variation due to charge/discharge is reduced. The present disclosure achieves the object by providing a method for producing an active material, the method comprising steps of: a preparing step of preparing a LiSi precursor including a Si element and a Li element, and a void forming step of forming a void by extracting the Li element from the LiSi precursor by using a Li extracting solvent, and the LiSi precursor includes a crystal phase of Li22Si5.