An optical device for splitting a single beam to a plurality of beams and an exposure apparatus including the optical device are disclosed. The optical device includes a first DOE lens array including a plurality of first diffractive optical element (DOE) lenses that are two-dimensionally arranged on a first plane and a second lens array including a plurality of second DOE lenses arranged on a second plane parallel to the first plane so as to respectively correspond to the plurality of first DOE lenses. The first DOE lens array splits a first parallel beam into a plurality of second beams by condensing the first parallel beam and the second DOE lens array modifies the plurality of second beams into a plurality of third beams.