Disclosed are a lens barrel capable of preventing a reduction in strength while maintaining a small size and a small thickness and an imaging apparatus including the lens barrel. A first moving cylinder in which a cam groove to which a second cam follower pin is fitted is provided in an inner surface is arranged outside a cam cylinder having the second cam follower pin provided on an outer surface thereof. In addition, a third lens group frame in which a cam follower pin fitted to one of the cam grooves is provided on an outer surface and a second lens group frame in which a cam follower pin fitted to the other groove is provided on an outer surface are arranged inside the cam cylinder having the cam grooves provided in the inner surface thereof.