An imaging unit includes: a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; and a solid-state imaging device that images an optical image formed by the first lens group to the third lens group sequentially arranged from an object side toward an image side, wherein, at zooming from a wide-angle end to a telephoto end, a distance between the first lens group and the second lens group becomes larger and a distance between the second lens group and the third lens group becomes smaller, and a distance from the second lens group to the solid-state imaging device at the wide-angle end is the longest in all zoom positions.