Abstract: An aerosol generating device includes: a hollow casing comprising a path for accommodating a cigarette, an opening open to the outside at one end of the path such that the cigarette is inserted into the opening from the outside, a through hole connected to the other end of the path, and a protrusion protruding from the path to contact a portion of an outer surface of the cigarette; and a heater having one side end portion passing through the through hole and arranged inside the path to be inserted into the cigarette accommodated in the path, the heater being configured to heat the cigarette when electricity is applied.