A lens barrel of the present invention includes a fixed frame, a plurality of lens groups disposed on the inner circumference of the fixed frame movably along an optical axis direction with respect to the fixed frame, at least three lens holding frames for holding at least one lens group of a plurality of the lens groups, a cam frame having bottomed cam grooves to be coupled with the inner circumference of the fixed frame through cams, bottomed cam grooves across each other to be coupled with the lens holding frames through cams and a bottomed cam groove which is discontinued on one end surface and continued from the other end surface, a key member for regulating the rotation of the lens holding frames about an optical axis with respect to the fixed frame as well as reinforcing the strength of the entire lens barrel, a cam mechanism interposed between the cam frame and the lens holding frames for moving the lens holding frames along the optical axis direction by the rotation of the cam frame about the optical axis with respect to the fixed frame, an internal gear disposed on the inner circumference of the cam frame, a pinion gear for transmitting a drive force from a drive source to the internal gear, flexible printed substrates which are overlapped in a thickness direction with a uniform width so that they are electrically connected to lens frames moving in the optical axis direction, bent to a U-shape and not overlapped each other at the bent portions, rod members provided with the two lens holding frames disposed at both ends along the optical axis of the three lens holding frames, respectively and extending in a direction parallel with the optical axis, and bearings provided with the lens holding frame interposed between the two lens holding frames along the optical axis for receiving the rod members.