To make it possible to easily expose and reproduce a hologram of a wide half-value width without executing special treatment and without establishing intricate conditions by executing exposure while changing the wavelength of a wavelength variable light source.

The laser beam emitted from a wavelength variable laser 10 is bisected by a half mirror. The bisected beams are properly turned back by a mirror 12, then formed as divergent beams by the special filters 13 consisting of objective lenses and pinholes. The wave front of this time is spherical. The two beams interfere with each other and the interference fringes formed within the hologram 16 are recorded as the hologram when a hologram photosensitive material 16 stuck to a glass substrate 15 is irradiated with these two divergent beams. The hologram exposed by the two divergent beams turns to a holographic mirror. The mirror having magnification is produced by the ratio of the distances R1 and R2 between the respective special filters 13 and hologram photosensitive material 16 of this time.