A holographic device includes a holographic storage device, a shearing interferometer, and an optical receiver. The holographic storage device is configured to provide a disk with a reading light beam to make the reading light beam become a diffracted light beam after the reading light beam is diffracted in the disk. The shearing interferometer is configured to receive the diffracted light beam and to transform the diffracted light beam into a first light beam and a second light beam. The optical receiver is configured to receive the first light beam and the second light beam provided by the shearing interferometer.