For the first time the NMR technique has been applied to the investigation of photomagnetic phenomena in a magnetic material. In the transparent easy-plane weak ferromagnet FeBO₃ the ⁵⁷Fe NMR spectra were measured with and without light illumination. It was shown that the exposure to light leads to (i) a total NMR frequency shift, as a result of electronic magnetization change, and (ii) a NMR signal increase, which is spectrally inhomogeneous at small external magnetic fields, where NMR spectrum splitting exists. The suggested mechanism for signal enhancement was connected to the light induced decrease of the basic-plane magnetic anisotropy.