Provided is a production method of a β-sialon phosphor that europium ions are solid-solved in β-sialon, including a mixing process for mixing raw materials of the β-sialon phosphor; a burning process for burning the raw materials after the mixing process to form the β-sialon phosphor; a HIP treatment process in which the β-sialon phosphor after the burning process is subjected to a HIP treatment; an annealing process in which the β-sialon phosphor after the HIP treatment process is subjected to an annealing treatment; and an acid treatment process in which the β-sialon phosphor after the annealing process is subjected to an acid treatment. According to the production method of a β-sialon phosphor, a β-sialon phosphor excellent in luminescence intensity is obtained.