An aerosol-generating device is disclosed. The aerosol-generating device of the disclosure includes a cartridge having therein an insertion space formed to be elongated, a body coupled to the cartridge, a capacitance sensor disposed in the body so as to be adjacent to the insertion space in the cartridge coupled to the body, and a controller. The controller determines whether a stick is inserted into the insertion space based on a signal received from the capacitance sensor. When the stick is inserted into the insertion space, the controller determines whether the stick inserted into the insertion space is a used stick based on a signal received from the capacitance sensor.