Diffractive optical element and method for manufacturing same

In a diffractive optical element having a structure in which a base body and an optical adjustment layer are bonded, defects such as cracking and separation occur in the optical adjustment layer if the strength of adhesion of the base body and the optical adjustment layer decreases. In this diffractive optical element (100), a plurality of anchor grooves (3) is formed in a planar second region (6) of a base body (1). A structure is used in which the depth of the outermost anchor groove among the plurality of anchor grooves (3) is less than the depth of the innermost anchor groove. In the base body (1) thus configured, an optical adjustment layer (9) is bonded so as to cover a first region (5), in which a diffraction grating (2) is formed, and the second region (6), in which the anchor grooves (3) are formed.