A lens barrel has a base, a second lens holder frame holding a second lens group, a first lens holder frame holding a first lens group, a cam ring, and a fixed ring. The second lens holder frame has three guides projecting axially from an outer circumferential portion of an annular plate and disposed at circumferentially equally spaced intervals. Guide grooves are defined in respective portions of the annular plate which are radially inwardly faced by the guides. Guide posts engage respectively in the guide grooves, so that the second lens holder frame is nonrotatably, but axially movably supported by the guide posts.