A lens system for image pickup consisting of, in order from an object side: a first lens group that has negative refractive power and is fixed during focusing; a second lens group that has positive refractive power and moves during focusing; a third lens group that has positive refractive power and is fixed during focusing; and a fourth lens group that has a stop (St) disposed on the object side, is fixed during focusing, has positive refractive power, and is disposed closest to an image plane side, wherein the first lens group includes: a first lens with positive refractive power that is disposed closest to the object side; wherein the first lens group consists of, in order from an object side: a first sub-lens group (G1a) that has negative refractive power and includes the first lens and a lens with negative refractive power disposed closest to an image plane side; and a second sub-lens group (G1b) that has negative refractive power and is disposed on the image plane side with a distance apart from the first sub-lens group (G1a), and characterized in that a distance W0 along an optical axis from a surface that is closest to the object side in the first sub-lens group (G1a) to an image forming plane, a distance W1 along the optical axis from the surface that is closest to the object side to a surface that is closest to the image plane side in the first sub-lens group (G1a), and a distance W2 along the optical axis from the surface that is closest to the object side in the first sub-lens group (G1a) to a surface that is closest to the object side in the second sub-lens group (G1b) satisfy following conditions. 0.05 < W 1 / W 0 < 0.15 0.17 < W 2 / W 0 < 0.29. a first lens group that has negative refractive power and is fixed during focusing; a second lens group that has positive refractive power and moves during focusing; a third lens group that has positive refractive power and is fixed during focusing; and a fourth lens group that has a stop (St) disposed on the object side, is fixed during focusing, has positive refractive power, and is disposed closest to an image plane side, wherein the first lens group includes: a first lens with positive refractive power that is disposed closest to the object side; wherein the first lens group consists of, in order from an object side: a first sub-lens group (G1a) that has negative refractive power and includes the first lens and a lens with negative refractive power disposed closest to an image plane side; and a second sub-lens group (G1b) that has negative refractive power and is disposed on the image plane side with a distance apart from the first sub-lens group (G1a), and characterized in that a distance W0 along an optical axis from a surface that is closest to the object side in the first sub-lens group (G1a) to an image forming plane, a distance W1 along the optical axis from the surface that is closest to the object side to a surface that is closest to the image plane side in the first sub-lens group (G1a), and a distance W2 along the optical axis from the surface that is closest to the object side in the first sub-lens group (G1a) to a surface that is closest to the object side in the second sub-lens group (G1b) satisfy following conditions. 0.05 < W 1 / W 0 < 0.15 0.17 < W 2 / W 0 < 0.29. a first lens with positive refractive power that is disposed closest to the object side; wherein the first lens group consists of, in order from an object side: a first sub-lens group (G1a) that has negative refractive power and includes the first lens and a lens with negative refractive power disposed closest to an image plane side; and a second sub-lens group (G1b) that has negative refractive power and is disposed on the image plane side with a distance apart from the first sub-lens group (G1a), and characterized in that a distance W0 along an optical axis from a surface that is closest to the object side in the first sub-lens group (G1a) to an image forming plane, a distance W1 along the optical axis from the surface that is closest to the object side to a surface that is closest to the image plane side in the first sub-lens group (G1a), and a distance W2 along the optical axis from the surface that is closest to the object side in the first sub-lens group (G1a) to a surface that is closest to the object side in the second sub-lens group (G1b) satisfy following conditions. 0.05 < W 1 / W 0 < 0.15 0.17 < W 2 / W 0 < 0.29.