An aerosol generating device includes an accommodation portion configured to accommodate at least a portion of a cigarette, and a heater arranged in the accommodation portion to heat the cigarette. The heater may include a first heating portion arranged along the inside of the accommodation portion, a second heating portion arranged in a lower portion of the accommodation portion, and a third heating portion extending in a lengthwise direction of the cigarette from the lower portion of the accommodation portion, and the first heating portion, the second heating portion, and the third heating portion may be thermally connected to one another.