To prolong a back focus at a wide angle and to sufficiently correct a distortion aberration and the chromatic aberration of magnification by specifying a relation among the focal distances of a whole projective lens system and first-third lens groups and the air intervals of the respective lens groups.

A first lens group 1 has strong negative power and secures a back focus. A second lens group 2 has positive power and makes bounced light beams on an axis into almost parallel light beams. A third lens group has positive power. When the focal distance of the whole projective lens system is set to f0, the focal distance of the first to third lens groups 1-3 f1g-fg3, the air interval of the first and second lens groups 1 and 2 to d6, the air interval of the second and third lens groups 2 and 3 to d9, the air interval when a part between the trailing end of a final lens to an image face is set to be air to bf, the relation of expressions -0.8<f1g/f2g<-0.7, -0.5<(f1g-d6+f2g)/f0<-0.1, 0.85<bf/f3g<0.95 and 0.2<d9/f3g<0.4 is satisfied.