When a master hologram is formed, a diffusing screen image is made an object light beam and outputted onto a first recording surface (12) through a lens (8'). When a slave hologram is formed, a second recording surface (12'') is placed in a position where the object light beam is focused by the lens (8'). The distance between the diffusing screen (7') and the first recording surface (12) of when the master hologram (12') is formed can be different from the distance between the master hologram (12') and the second recording surface (12'') of when the slave hologram (12'') is formed. Therefore, as necessary, the distances are made different from each other, and thereby a hologram can be formed by means of a small optical system.