The invention discloses a device for automatically detecting the two-dimensional shape of a wafer substrate and belongs to the semiconductor material nondestructive detection technical field. In the device, a plurality of paths of emergent light of N laser beams are emitted by one laser and pass through a beam splitting prism including a plurality of beam splitting surfaces; the light intensities of the plurality of paths of emergent light emitted out from the beam splitting prism can be identical through endowing different reflectivity and transmissivity for the plurality of beam splitting surfaces, namely, the plurality of paths of emergent light with the same light intensity are not emitted by a plurality of lasers, but are obtained through reflecting and refracting the light emitted by one laser by means of the beam splitting prism, and therefore, in a limited arrangement space, a large-sized laser can be selected; when the size of the laser is increased, the inner heat dissipation performance of the laser can be improved; a feedback circuit is additionally arranged in the laser, the internal parameters of the laser can be changed according to needs; and thus, the output power and wavelength stability of the laser can be enhanced.