Lens barrel and electronic apparatus

A lens barrel holding a photographing optical system which is a zoom lens constituted by five groups of a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, a fourth lens group with negative refractive power and a fifth lens group with positive refractive power, the lens barrel being capable of shortening a total length thereof when not taking photographs, comprising:

• a cylindrical cam barrel arranged to be rotatable around an optical axis;
• a first lens driving section driving the cam barrel around the optical axis at a time of a magnification changing operation of the photographing optical system;
• a plurality of first cam grooves carved on an outer circumferential surface of the cam barrel;
• and
• a plurality of second cam grooves carved on an inner circumferential surface of the cam barrel;
• wherein
• a first lens group holding barrel holding the first lens group has a plurality of cam followers that are recessed in the first cam grooves;
• and
• each of a second lens group holding barrel holding the second lens group and a third lens group holding barrel holding the third lens group has a plurality of cam followers that are recessed in the second cam grooves.