A diffractive optical element, in which a diffraction grating having a large pitch and a multitude of diffraction gratings can be arranged, includes a plurality of cells arranged side by side, wherein, for each cell, the pitch at which projections are lined up and/or the orientation of an in-plane rotation direction are/is different, and, within a single cell, the projections' pitch and the in-plane rotation direction orientation are the same, the diffractive optical element shaping light by this configuration which is an assembly of these cells. The plurality of cells include: a plurality of basic cells having the same outer shape; and a composite cell having a different outer shape from the basic cells, formed such that the length thereof in a specific direction is longer than the length of the basic cell, the composite cell having a diffraction grating including at least a single pitch's worth of the projection(s).