A method of generating a single photon, includes preparing an optical resonator including a resonator mode of a resonance angular frequency ωc, preparing a material contained in the optical resonator, including a low energy state |g> and a high energy state |e>, and including a transition angular frequency ωa between |g>−|e> that is varied by an external field, applying, to the material, light of an angular frequency ωl different from the resonance angular frequency ωc, and applying a first external field to the material to vary the transition angular frequency ωa to resonate with the angular frequency ωl, such that a state of the material is changed to |e>, and then applying a second external field to the material to vary the transition angular frequency ωa to resonate with the resonance angular frequency ωc, such that the state of the material is restored to |g>.