Provided is a method of producing semiconductor nanoparticles that exhibit a band-edge emission, and are superior in quantum yield. The method includes raising the temperature of a first mixture containing a silver (Ag) salt, a salt containing at least one of indium (In) and gallium (Ga), a solid compound that serves as a supply source of sulfur (S), and an organic solvent to a temperature in a range of from 125° C. to 175° C., and heat-treating, subsequent to the raising of the temperature, the first mixture at a temperature in a range of from 125° C. to 175° C. for three seconds or more to obtain a solution containing semiconductor nanoparticles, and decreasing the temperature of the solution containing semiconductor nanoparticles. The solid compound that serves as a supply source of S contains thiourea.