Provided is a single-phase stress light-emitting material which is capable of emitting light with high sensitivity even under small stress, and uses a piezoelectric material as a host material. The single-phase stress light-emitting material is characterized in that some of the Li atoms constituting a LiNbO3 crystal are substituted by at least one kind of metal ion selected from among rare earth metal ions and transition metal ions. The single-phase stress light-emitting material is also characterized by having a nonstoichiometric composition represented by general formula LixNbO3 : My, wherein : x=1-y and 0.0001≤y≤0.2, or x>1-y and 0.0001≤y≤0.2; 0.8
