The method of the production of a nanoparticle of the present invention includes a step of forming a nanoparticle of a group II - group VI compound semiconductor in the cavity part of a protein, in a solution containing the protein having a cavity part therein represented by apoferritin, the group II element ion represented by Cd and Zn, and the group VI element ion represented by S and Se. Preferably, the solution further includes an ammonium ion, and the supply of the group VI element ion (X 2- ) into the solution is conducted by adding H2NCXNH2 to the solution. According to the aforementioned method, semiconductor nanoparticles having a uniform particle size can be produced. <IMAGE>