An aerosol generating device comprising: a case into which a cigarette is insertable; and a controller for controlling an operation of the aerosol generating device, wherein the case includes: a cap coupled to a top portion of the case to be detachable from the case; a cover located on a top surface of the cap and configured to open and close a cigarette insertion hole into which the cigarette is insertable; a sensor configured to sense whether the cigarette insertion hole is open or closed; and a button configured to receive a user's input according to manipulation of a user, wherein the controller is configured to: control the operation of the aerosol generating device based on a signal by the sensor and the button, characterized in that the controller is configured such that when it is determined that the cigarette insertion hole is open, a preliminary heating operation of the aerosol generating device is performed as the button is pressing-manipulated during a first pressing time; and when it is determined that the cigarette insertion hole is closed, the preliminary heating operation of the aerosol generating device is not performed even when the button is pressing-manipulated during the first pressing time. a case into which a cigarette is insertable; and a controller for controlling an operation of the aerosol generating device, wherein the case includes: a cap coupled to a top portion of the case to be detachable from the case; a cover located on a top surface of the cap and configured to open and close a cigarette insertion hole into which the cigarette is insertable; a sensor configured to sense whether the cigarette insertion hole is open or closed; and a button configured to receive a user's input according to manipulation of a user, wherein the controller is configured to: control the operation of the aerosol generating device based on a signal by the sensor and the button, characterized in that the controller is configured such that when it is determined that the cigarette insertion hole is open, a preliminary heating operation of the aerosol generating device is performed as the button is pressing-manipulated during a first pressing time; and when it is determined that the cigarette insertion hole is closed, the preliminary heating operation of the aerosol generating device is not performed even when the button is pressing-manipulated during the first pressing time. a cap coupled to a top portion of the case to be detachable from the case; a cover located on a top surface of the cap and configured to open and close a cigarette insertion hole into which the cigarette is insertable; a sensor configured to sense whether the cigarette insertion hole is open or closed; and a button configured to receive a user's input according to manipulation of a user, wherein the controller is configured to: control the operation of the aerosol generating device based on a signal by the sensor and the button, characterized in that the controller is configured such that when it is determined that the cigarette insertion hole is open, a preliminary heating operation of the aerosol generating device is performed as the button is pressing-manipulated during a first pressing time; and when it is determined that the cigarette insertion hole is closed, the preliminary heating operation of the aerosol generating device is not performed even when the button is pressing-manipulated during the first pressing time. control the operation of the aerosol generating device based on a signal by the sensor and the button, characterized in that the controller is configured such that when it is determined that the cigarette insertion hole is open, a preliminary heating operation of the aerosol generating device is performed as the button is pressing-manipulated during a first pressing time; and when it is determined that the cigarette insertion hole is closed, the preliminary heating operation of the aerosol generating device is not performed even when the button is pressing-manipulated during the first pressing time.