To obtain an objective for an endoscope which has specified 4-group, 5-element constitution and also has excellent optical performance by excellently correcting aberrations, specially, a power chromatic aberration while having a wide angle of about 135 to 140° and securing necessary back focus by satisfying all conditional expressions.

The objective comprises a 1st negative lens L1 which is concave to the iamge side, a 2nd positive lens L2 which has a plane on the image side, a lightness stop 3, a 3rd positive lens L3 which has a larger-curvature-diameter surface on the object side, and a doublets L4+5 which is composed of a 4th positive lens L4 which has a larger-curvature-radius surface on the object side and a 5th negative meniscus lens L5 and has positive refracting power, and satisfies (1) 1.50<|d/f1'|<2.50, (2) 0.96<f'/h<1.04, and (3) 12.0<f'×(ν4-ν5)/(Rc×Bf') (where d is the distance from the concave surface peak of the 1st lens L1 to the stop 3, h is the maximum image height, and Rc is the absolute value of the radius of curvature of the joined surface).