To compensate the deterioration of image forming performance caused by the deformation of a diffraction optical element and to maintain the optical performance by setting the pitch of a diffraction grating so that the change of the optical characteristics after the diffraction optical element has been deformed from its ideal shape may be compensated.

The diffraction optical element 101 is formed on a transparent base plate 103 or on the surface of the plate 103. The diffraction optical element 108 is formed on the surface 102 side of the diffraction optical element 101. The diffraction optical element 101 in a state where deformation by gravity is not caused is shown in figure A, and the diffraction optical element 106 in a state where the deformation by gravity is caused is shown in figure B, then, the diffraction optical element 107 in a state where the pitch and the shape of the diffraction grating are reset so that the change of the optical performance caused by the deformation by gravity in figure B may be compensated is shown in figure C. The aberration occuring, when the diffraction optical element 101 having positive power (refractive power) causes the deformation such as the deformation by gravity or lens barrel pressing deformation and its shape getting out of the ideal shape, is compensated by resetting the grating pitch of the diffraction grating.