To provide a condenser lens system having compact structure, which is incorporated in a narrow space and selectively emits inspection light of a specified wavelength region, and an illuminator.

The condenser lens system condenses wavelength light of a wide band emitted from a light source (2a) and selectively emits wavelength light of a predetermined wavelength band as focused light beam. The condenser lens system successively includes a first positive lens (20), a wavelength selection filter (21) selectively transmitting the wavelength light of the specified wavelength region, a negative lens (22) and a second positive lens (23). Alternatively, two negative lenses (31 and 33) are arranged between the first positive lens and the second positive lens, and a wavelength selection filter (32) is arranged between the negative lenses. Even if illuminating light emitted from the light source obliquely enters the wavelength selection filter to cause aberration, the aberration is corrected by the negative lens at a subsequent stage. As a result, the condenser lens system having short optical path length is obtained.