To provide an endoscope objective lens which has a lens constitution of a relatively small number of three pieces, a short total length of lens, and various kinds of good optical performances starting with curvature of field. It is constituted of a first lens L.sub.1 directing its concave surface to the image side, a second lens L.sub.2 made of a positive meniscus lens directing its convex surface to the image side, and a third lens L.sub.3 made of a planoconvex lens directing its convex surface to the object side arranged sequentially from the object side, and a stop placed between said first lens L.sub.1 and said second lens L.sub.2. It also satisfies the following Conditional Expressions: 2.00<|f.sub.1/f|<3.00, (1) 0.50<|f.sub.2/f.sub.3|<0.70, (2) 2.00<|f.sub.1/d.sub.1-2|<5.00 , (3) 0.40<|R.sub.2R/R.sub.2F|<0.60 . (4) Note that f is the focal length of the whole system, f.sub.1 f.sub.3 the focal lengths of the first-third lenses, respectively, d.sub.1-2 the air distance between the first lens and the second lens, R.sub.2F the radius of curvature of the object-side surface of the second lens, and R.sub.2R the radius of curvature of the image-side surface of the second lens.