A main body unit for an aerosol generation device, the main body unit being at least dividable into a first unit and a second unit, comprising: a rotation connection mechanism configured to connect the first unit and the second unit by inserting an engagement convex portion disposed in either of the first unit or the second unit into an engagement groove portion disposed in the other one of the first unit or the second unit and rotating in a first rotation direction around a central axis of the main body unit; a first convex portion disposed in either of the first unit or the second unit, the first convex portion protruding outwardly in a radial direction orthogonal to the central axis; and a second convex portion disposed in the other of the first unit or the second unit, the second convex portion protruding inwardly in the radial direction, wherein when a connection is performed in the rotation connection mechanism, either of the first convex portion or the second convex portion is elastically deformed in the radial direction while climbing over the other one of the first convex portion or the second convex portion and engaged with the other one of the first convex portion or the second convex portion in a second rotation direction opposite to the first rotation direction; the main body unit being characterized in that: the engagement convex portion and the engagement groove portion are engaged with each other to finish a position alignment of the first unit and the second unit in an axial direction of the main body unit, and the first convex portion and the second convex portion are engaged with each other to finish a position alignment of the first unit and the second unit in a circumferential direction of the main body unit. a rotation connection mechanism configured to connect the first unit and the second unit by inserting an engagement convex portion disposed in either of the first unit or the second unit into an engagement groove portion disposed in the other one of the first unit or the second unit and rotating in a first rotation direction around a central axis of the main body unit; a first convex portion disposed in either of the first unit or the second unit, the first convex portion protruding outwardly in a radial direction orthogonal to the central axis; and a second convex portion disposed in the other of the first unit or the second unit, the second convex portion protruding inwardly in the radial direction, wherein when a connection is performed in the rotation connection mechanism, either of the first convex portion or the second convex portion is elastically deformed in the radial direction while climbing over the other one of the first convex portion or the second convex portion and engaged with the other one of the first convex portion or the second convex portion in a second rotation direction opposite to the first rotation direction; the main body unit being characterized in that: the engagement convex portion and the engagement groove portion are engaged with each other to finish a position alignment of the first unit and the second unit in an axial direction of the main body unit, and the first convex portion and the second convex portion are engaged with each other to finish a position alignment of the first unit and the second unit in a circumferential direction of the main body unit. the engagement convex portion and the engagement groove portion are engaged with each other to finish a position alignment of the first unit and the second unit in an axial direction of the main body unit, and the first convex portion and the second convex portion are engaged with each other to finish a position alignment of the first unit and the second unit in a circumferential direction of the main body unit.