An aerosol-generating device. The cavity defined together by the storage portion and the mouthpiece for accommodating the aerosol-generating substrate can effectively fix the aerosol-generating substrate, hereby preventing the aerosol-generating substrate or a tobacco residue from falling during a smoking process. In addition, when a user directly pulls an extractor out of a main body, that is, the storage portion and the mouthpiece are subjected to an axially force, the mouthpiece can radially expand outward such that the mouthpiece is separated from the storage portion. Before the extractor is detached from the main body, the main body would restrict the end of the mouthpiece adjacent to the main body from radially expanding outward.