An objective optical system for endoscope includes, a first group having a positive refractive power, an aperture stop, and a second group having a positive refractive power, wherein the first group includes a first lens having a negative refractive power, and a second lens having a positive refractive power, the second group includes a cemented lens, and the cemented lens includes a third lens having a positive refractive power and a fourth lens having a negative refractive power, and the following conditional expressions (1), (2), (3), (4), (7) and (9) are satisfied:0.13≦La/Lb≦0.17 (1),−2.7≦f4/f≦−2.2 (2),−0.7≦(ne2×f2)/(ne4×f4)≦0 (3),2.5≦νd3/νd4≦3.5 (4)−2.6≦r2o/rcc≦−2 (7), and−1.2≦r2i/f2≦−0.9 (9).
