A simple two-group zoom optical system that favorably corrects aberrations includes, in order from the object side, a first lens group of negative refractive power, a stop, and a second lens group of positive refractive power. The first lens group includes, in order from the object side, a lens element having negative refractive power and a meniscus shape with its concave surface on the image side, a biconcave lens element, and a lens element having positive refractive power. The second lens group includes, in order from the object side, a lens element having positive refractive power and at least one aspheric surface, a lens element having negative refractive power, and a biconvex lens element. Certain conditions are satisfied that relate to the focal lengths of the zoom optical system, the focal lengths of the two lens groups, and to the Abbe numbers of lens elements.