A diffractive optical element includes at least a first diffractive
element and a second diffractive element. The conditional expression
0.5.ltoreq.D/DS.ltoreq.0.9 is preferably satisfied where DS denotes the
summation of the optimum designed groove height of the first diffractive
element d1S and that of the second diffractive element d2S, and D denotes
the summation of an actual groove height of the first diffractive element
d1 and that of the second diffractive element d2. At least one of the
first diffractive element and the second diffractive element is made of
glass. At least one of the first diffractive element and the second
diffractive element is made of resin. The optimum designed value of
groove heights of the diffractive optical element are determined so as to
satisfy a condition for correcting chromatic aberration at both d-line
and g-line.