To provide a diffractive optical element having a high light utilization efficiency, whereby light spots having a predetermined pattern can be stably formed, a projection device and a measuring device.
The diffractive optical element of the present invention comprises a transparent substrate, a convexo-concave portion formed so as to be in contact with one surface of the transparent substrate and a filling portion with which concave portions of the convexo-concave portions are filled and which covers top surfaces of convex portions of the convexo-concave portion for planarizing the convexo-concave portion, wherein the convexo-concave portion has at least two stages on the surface of the transparent substrate; the top surfaces of the respective stages are parallel to one another; among the transparent substrate, the convexo-concave portion and the filling portion, the refractive indexes of at least the convexo-concave portion and the filling portion are different with respect to the incident light which enters from the normal direction of the surface of the transparent substrate; and the refractive indexes of the transparent substrate, the convexo-concave portion and the filling portion with respect to incident light are at most 2.2.