A lens barrel includes a lens holding frame configured to hold a lens and being provided with a cam follower, a guide tube engaging with the lens holding frame and being configured to rectilinearly guide the lens holding frame in an optical axis direction, and a cam tube engaging with the cam follower and being provided with a cam slot which engages with the cam follower, the cam tube being configured to rotate about the optical axis thereby to move the lens holding member in the optical axis direction, wherein the cam slot has a locus including a flat portion orthogonal to the optical axis and a lift portion not orthogonal to the optical axis, wherein the flat portion has a surface perpendicular to the optical axis, and wherein the cam follower has a surface parallel to the perpendicular surface.