In a lens unit 1, and an image sensing apparatus 15 incorporated with the lens unit 1 of the invention, a fixed cylinder 2 is formed with an oblong hole 21 extending in an optical axis direction in a lateral surface of the fixed cylinder 2. A driving force from a driving member such as a motor 12 is transmitted to a gear portion formed on an outer periphery of a cam cylinder 3 by a major axis gear 10 received in the oblong hole 21. Thereby, the cam cylinder 3 is rotated, and a lens holding frame is driven in the optical axis direction for a zoom operation. A pressing member 13 for pressing the major axis gear 10 in the optical axis direction during the zoom operation is provided at an end surface of the major axis gear 10.