To provide an anamorphic prism with which the intensity distribution of a beam on a recording medium can be easily varied and recording and reproducing can be carried out in the optimum state without increasing the size of the device, and to provide an optical head and an optical recording and reproducing device small in size and having high productivity which use the anamorphic prism.

The anamorphic prism is produced by joining and integrating a first prism 2 consisting of a first medium and a second prism 3 consisting of a second medium on specified faces as joining faces. The prism has such functions that the light entering the first prism 2 is enlarged or reduced by a specified magnification in a specified direction in the cross section of the beam and that the enlarged or reduced light is made to exit from the second prism 3 as an exiting beam having the propagation direction almost parallel to the propagation direction of the incident beam propagating to the first prism 2.