A single-focal lens system includes a first lens group having positive power, an aperture diaphragm, and a second lens group having positive power, in this order from an object side to an image side. The first lens group includes a first lens element having negative power, a second lens element having negative power, and a third lens element having positive power in this order from the object side to the image side. The second lens group includes a fourth lens element having power and a fifth lens element having positive power. When fG1 is a focal length of the first lens group at a d-line, fG2 is a focal length of the second lens group at the d-line, f4 is a focal length of the fourth lens element at the d-line, f is a focal length of an entire system at the d-line, and w is a half angle of view, a condition (1), a condition (3c) and a condition (6) shown below are satisfied. 0.5