An optical system (10) for image pickup includes a first refractive optical system (Si) disposed on an object side with respect to an aperture stop (St) and a second refractive optical system (S2) disposed on an image plane side with respect to the aperture stop. The first refractive optical system includes, in order from the object side (11), a first lens group (G1) with positive refractive power, a second lens group (G2) with positive refractive power, and a third lens group (G3) with negative refractive power. The second refractive optical system includes, in order from the object side (11), a fourth lens group (G4) with positive refractive power, a fifth lens group (G5) with positive refractive power, and a sixth lens group (G6) with negative refractive power. When focusing from infinity to a short distance, the second lens group and the fourth lens group move toward the object side.