An optical system of the present invention includes, in order from an object side: a first lens group G1; a second lens group G2 having positive refractive power; and a third lens group G3 having positive refractive power, wherein the first lens group G1 and the third lens group G3 are fixed in an optical axis direction while the second lens group G2 is moved in an optical axis direction to focus on from an object at infinity to an object at a finite distance, and specified conditions is satisfied.