PURPOSE: To make a lens barrel thinner and to drive a lens with high accuracy and high speed by efficiently arranging a cylindrical stepping motor in the lens barrel.

CONSTITUTION: A small-diameter front-group lens 11 is fixedly arranged in front of a diaphragm position B in the lens barrel 10 and a large-diameter rear-group lens 12 is arranged to move forward and backward in the direction of an optical axis A in a rear side. The rear-group lens 12 has a shape that its lower part is cut off. A two-blade shutter served also as a diaphragm which is driven to open/close in a range where the shutter does not interfere with the cut off part of the rear-group lens 11 is arranged in the diaphragm position B. In the spaces 23 and 24 of the lower sides of the rear- and front-group lenses 12 and 11, the cylindrical stepping motor 25 is arranged to cross the diaphragm position B.