A third group of lenses is constructed by subsequently arranging those four lenses from an object side to an image side which include a positive lens, a cemented lens of a positive lens and a negative lens, and a positive lens, both of a surface of the third group of the lenses nearest to the object side and a surface of the third group of the lenses nearest to the image side are so aspheric that positive refractive power becomes gradually weaker as a location of the third group of the lenses departs from an optical axis; and a following conditional formula is satisfied: -0.5<(Y' max/R.sub.34I)<0.0 where R.sub.34I is a curvature radius of the surface of the third group of the lenses nearest to the image side, and Y' max is a maximum image height.