There is provided an objective lens capable of reducing the effects of magnetic fields on a sample. The objective lens includes a first lens and a second lens. The lenses are arranged so that the component of the magnetic field of the first lens lying along the optical axis and the component of the magnetic field of the second lens lying along the optical axis cancel out each other at a sample placement surface. The first and second lenses each include an inner polepiece and an outer polepiece. The inner polepieces have front end portions, respectively. The outer polepieces have front end portions, respectively, which jut out toward the optical axis. The distances of the front end portions of the outer polepieces, respectively, from the sample placement surface are less than the distances of the front end portions of the inner polepieces, respectively, from the sample placement surface.