To obtain a microlens with which photographing from infinity near to a life size is possible without changing its overall length and which has high performance and excellent operability by constituting the microlens in such a manner that the focal lengths of respective lens groups satisfy specific conditions.

This microlens has, successively from an object side, a first lens group G1 including a negative lens and having positive refracting power, a second lens group G2 including a cemented lens and having negative refracting power, a third lens group G3 including a cemented lens and having negative refracting power and a fourth lens group G4 having positive refracting power. The long-focus microlens satisfies the respective conditions -5<f2/f1<-2, 2.5<f2/f3<7.5, 1<f4/f1<2. In the equations, f1 denotes the focal length of the first lens group G1, f2 the focal length of the second lens group G2, f3 the focal length of the third lens group G3 and f3 the focal length of the fourth lens group G4, respectively.