Provided is an aerosol generation device including: a case into which a cigarette is insertable; a heater arranged in the case and configured to heat the cigarette inserted into the case; a mainstream smoke passage connecting an internal end portion of the cigarette to the outside; and a vaporizer configured to heat a liquid composition to generate aerosol and deliver the aerosol to the mainstream smoke passage, wherein at least a portion of the mainstream smoke passage extends in a direction crossing a longitudinal direction of the cigarette.