A method for controlling recombination lifetime for controlling recombination lifetime of carriers in a silicon single crystal substrate by performing: a preparation step of preparing a silicon single crystal substrate from a nitrogen-added silicon single crystal grown by a floating zone melting method (FZ method); a heat treatment step A of heat-treating the prepared silicon single crystal substrate; a particle beam irradiation step of irradiating the silicon single crystal substrate after the heat treatment step A with a particle beam; and a heat treatment step B of heat-treating the silicon single crystal substrate after the particle beam irradiation step, wherein in the heat treatment step A, a nitrogen concentration Cn of the silicon single crystal substrate is adjusted in the heat treatment by outwardly diffusing nitrogen in the silicon single crystal substrate in accordance with an oxygen concentration Co of the silicon single crystal substrate prepared in the preparation step, then the particle beam irradiation step is performed on the silicon single crystal substrate with the adjusted nitrogen concentration Cn, wherein when the oxygen concentration Co of the silicon single crystal substrate prepared in the preparation step is less than 0.1 ppma, in the heat treatment step A, the heat treatment is performed to outwardly diffuse nitrogen so that the nitrogen concentration Cn of the silicon single crystal substrate after the heat treatment step A becomes less than 2×10 14 atoms/cm 3 , and when the oxygen concentration Co of the silicon single crystal substrate prepared in the preparation step is 0.1 ppma or more, in the heat treatment step A, the heat treatment is performed to outwardly diffuse nitrogen so that the nitrogen concentration Cn of the silicon single crystal substrate after the heat treatment step A becomes less than 2×10 15 atoms/cm 3 , and then the particle beam irradiation step is performed. a preparation step of preparing a silicon single crystal substrate from a nitrogen-added silicon single crystal grown by a floating zone melting method (FZ method); a heat treatment step A of heat-treating the prepared silicon single crystal substrate; a particle beam irradiation step of irradiating the silicon single crystal substrate after the heat treatment step A with a particle beam; and a heat treatment step B of heat-treating the silicon single crystal substrate after the particle beam irradiation step, wherein in the heat treatment step A, a nitrogen concentration Cn of the silicon single crystal substrate is adjusted in the heat treatment by outwardly diffusing nitrogen in the silicon single crystal substrate in accordance with an oxygen concentration Co of the silicon single crystal substrate prepared in the preparation step, then the particle beam irradiation step is performed on the silicon single crystal substrate with the adjusted nitrogen concentration Cn, wherein when the oxygen concentration Co of the silicon single crystal substrate prepared in the preparation step is less than 0.1 ppma, in the heat treatment step A, the heat treatment is performed to outwardly diffuse nitrogen so that the nitrogen concentration Cn of the silicon single crystal substrate after the heat treatment step A becomes less than 2×10 14 atoms/cm 3 , and when the oxygen concentration Co of the silicon single crystal substrate prepared in the preparation step is 0.1 ppma or more, in the heat treatment step A, the heat treatment is performed to outwardly diffuse nitrogen so that the nitrogen concentration Cn of the silicon single crystal substrate after the heat treatment step A becomes less than 2×10 15 atoms/cm 3 , and then the particle beam irradiation step is performed. <EOS>