To reduce the complexity, thickness and size of a lens driver.

The lens driver includes: a base 10 having a cylindrical section 11; a lens holding frame 20 reciprocally supported relative to the cylindrical section in the optical axis direction, and having a follower pin 23 on an outer circumference; a cam cylinder 30 supported so as to turn around the optical axis relative to the cylindrical section, and having a cam groove 33 for applying a cam action to the follower pin in the optical axis direction; and a biasing spring 40 disposed between the lens holding frame and the base. The cylindrical section 11 has: an outer circumference 11a with the cam cylinder externally fitted from one side of the optical axis direction so as to be turnably supported; an inner circumference 11b with the lens holding frame internally fitted from the other side of the optical axis direction so as to be reciprocally supported; and a guide slit 14 for guiding the follower pin in the optical axis direction. The cam cylinder 30 has an introduction groove 34 for guiding the follower pin passing though the guide slit to the cam groove 33 while the cam cylinder 30 is externally fitted to the cylindrical section. The number of components is reduced. The complexity, thickness and size of a structure can be reduced.