A zoom lens apparatus is provided. In the zoom lens apparatus, rotation of a motor is transmitted to a cam drive gear by reducing a speed thereof by a plurality of reduction gears. The cam drive gear transmits rotation thereof to a zoom cam provided coaxially therewith. A first lens group and a second lens group are moved in an optical axis direction by rotation of the zoom cam to carry out zoom adjusting. An interval between the cam drive gear and the zoom cam is provided with a nontransmitting section in which rotation of the cam drive gear is not transmitted to the zoom cam when a rotational direction of the cam drive gear is switched, by rotation of the cam drive gear in the nontransmitting section, the zoom cam is slid in an axial direction. Thereby, also the first lens group and the second lens group connected and engaged with the zoom cam are moved in the optical axis direction along therewith to adjust a focus.