When a teleconverter is attached, the variator is once moved to the tele end regardless of its position. Thereafter, by the input of zoom operation key, the movement of the variator to the wide side, namely zooming, becomes possible with the range of movement automatically limited in a prescribed range in order to prevent shading due to the attachment of the teleconverter. Meanwhile, if a wide converter is attached, the variator is similarly moved to the wide end. Thereafter, the movement of the variator is prohibited regardless of the presence/absence of the input of the zoom operation key. When the teleconverter or the wide converter is detached, the limit of the range of movement or prohibition of the movement of the variator is cancelled and usual zooming operation is retrieved.