To make an image forming lens small, have a viewing angle larger than 150°, a bright Fno of 1.8 or smaller, a sufficiently long back focal length and good resolving power while composing it of five lenses.

First-five lenses L1-L5 have negative, negative, positive, positive and negative refractive powers in order from the object side. These lenses satisfy: 3.4≤(d4+d5)/h≤7.5 (d4: the interval between a second lens and a third lens, d5: the thickness of the third lens, f: the composite focal distance of the whole system). By satisfying the relation, spherical aberration, distortion and coma aberrations are compensated well and sufficient performance is obtained. This image forming lens has a long back focal length, a wide viewing angle ωof about 80°, bright Fno of 1.8, a small size and the good resolving power.