To provide a hologram recording and reproducing device which can be downsized.

The hologram recording and reproducing device has a supporting means which freely mountably holds and rotates a recording medium consisting of a photorefractive crystal having a parallel flat plate shape, a reference light means which makes a coherent recording reference light beam incident on the main surface of the recording medium, a signal light means which makes the coherent signal light beam modulated according to image data incident on the recording medium and intersects this beam with the recording reference light beam within the recording medium to form the refractive index grating of the light interference patterns of the signal light beam and the recording reference light beam, a means which makes the coherent reproducing reference light beam propagated in an opposite direction coaxially with the recording reference light beam incident on the recording medium and generate phase conjugation waves from the refractive index grating of the light interference patterns, a detecting means which separates the phase conjugation waves from the optical path of the signal light beam and a detecting means which detects the image data formed by the phase conjugation waves.