PROBLEM TO BE SOLVED: To attain excellent optical performance with simple constitution and to obtain high throughput. SOLUTION: A projection optical system projecting an image of a first object 10 onto a second object 30 at a substantially size-for-size magnification is provided with a positive lens group G1P having positive refractive force, a negative lens group G1N having negative refractive force and a concave reflection mirror M1. The positive lens group, the negative lens group and the concave reflection mirror are positioned so that a beam from the first object 10 arrives at the concave reflection mirror through successively the positive lens group and the negative lens group, and the beam reflected by the concave reflection mirror goes to the second object through successively the negative lens group and the positive lens group, and the first and second object sides become telecentric. At this time, the positive lens group contains at least the lens consisting of fluorite and having the positive refractive force, and the lens consisting of synthetic quartz and having the negative force, and the negative lens group contains the lens consisting of fluorite and having the negative force.
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