PURPOSE: To increase the degree of freedom in the design of a straight advance guide, etc., and to miniaturize a camera by arranging a cam follower fixed to a lens frame holding a photographing lens so that it is kept away from a diagonal direction on a photographic image frame.

CONSTITUTION: The dam followers 3a, 3b and 3c of the 1st lens frame 3 and the cam followers 4a, 4b and 4c of the 2nd lens frame are arranged at the position kept away from the diagonal direction of the photographic image frame 5. Therefore, the straight advance groove of a straight advance guide barrel 2 in which the cam followers 3a, 3b, 3c, 4a, 4b and 4c are fitted is also provided at the position kept away from the diagonal direction of the photographic image frame 5. Notches 2a, 2b and 2c are provided in the diagonal direction of the image frame 5 on the guide barrel 2, so that a photographic optical path is not blocked. Even when the diameters of the guide barrel 2 and a cam barrel 1 are made small, the photographic optical path is not blocked, and a zoom lens barrel is miniaturized.