An apparatus for exposing a plurality of lots of substrates to light. The apparatus includes a designating unit for designating, on the basis of an exposure condition being related to two consecutive lots of the plurality of lots of substrates and being reserved in the apparatus, an exposure preparation process being related to the latter one of the two consecutive lots and going to be omitted. The apparatus further includes an estimating unit for estimating a process time to be saved by the omission of the exposure preparation process designated by the designating unit, and a generating unit for generating a sequence for the plurality of lots, on the basis of the estimation made by the estimating unit, so as to minimize a required process time.