Disclosed herein is an apparatus for generating a parallel beam with a high flux. The apparatus of the present invention includes a light source, a first mirror and a second mirror. The light source is positioned at a first focal point of a first ellipse. The first mirror is positioned on the first ellipse to reflect a beam emitted by the light source, and concavely shaped to conform to a section of the first ellipse. The second mirror is positioned across a path of the beam reflected by the first mirror, and convexly shaped to conform to a section of a second ellipse so that an angle formed by two tangent lines passing through each pair of incident points of neighboring rays incident upon the second mirror, respectively, is half of an angle formed by two tangent lines passing through each pair of incident points of neighboring rays incident upon the first mirror, respectively.