A lens barrel is retractable in electronic equipment having an image-generating device, such as a CCD. During photographing, the lens barrel relocates a first lens group and a second lens group to a predetermined position in an optical axis to zoom the image of an object. During collapsing, the first lens group and the second lens group adjacent to the object side are transferred to a side of a CCD which is away from the optical axis and a focus driving mechanism drives the third lens group along the optical axis. The focus driving mechanism is disposed inside the lens barrel.