Provided is a method for producing a semiconductor nanoparticle including preparing a mixture containing a Ag salt, a salt containing at least one of In and Ga, and an organic solvent; raising the temperature of the mixture to a raised temperature in a range of from 120° C. to 300° C.; and adding a supply source of S to the mixture at the raised temperature in such a manner that a ratio of a number of S atoms to a number of Ag atoms in the mixture increases at a rate of not more than 10/min.