To excellently correct a chromatic aberration, and read a color document with high definition by arranging positive first lens and second lens, negative third lens and fourth lens and positive fifth lens and sixth lens in this order from the object side, and satisfying a specific condition.

Positive first and second lenses, negative third and fourth lenses and positive fifth and sixth lenses are arranged in this order from the object side. One lens material in the first and the second lenses satisfies an expression I, and one lens material in the fifth and the sixth lenses satisfies an expression II. A lens shorter in a focal distance in lenses to satisfy the expression I satisfies an expression III, and a lens shorter in a focal distance in lenses to satisfy the expression II satisfies an expression IV. In the expressions, (f) is a focal distance of the whole system, and (fa) is a focal distance of the first or the second lens, and (fb) is a focal distance of the fifth or the sixth lens, and Nda and Ndb are a refractive index of a construction material of the lenses, and νda and νdb are the Abbe's number of a construction material of the lenses.