A microparticle sorting device comprising: circuitry configured to: obtain optical information indicating a first microparticle population and a second microparticle population; control, based on light from the microparticles detected by a detection unit in response to irradiating the microparticles with excitation light as the microparticles flow through a main flow channel and based on a predetermined ratio or range of ratios of the first microparticle population and the second microparticle population, a sorting part to perform sorting of a first group of microparticles belonging to the first microparticle population and a second group of microparticles belonging to the second microparticle population to obtain a mixture of microparticles including microparticles both from the first microparticle population and the second microparticle population in a particle sorting flow channel coaxial with the main flow channel according to the predetermined ratio or range of ratios, the first group of microparticles being determined as belonging in the first microparticle population and the second group of microparticles being determined as belonging in the second microparticle population based on at least one characteristic of the detected light and the optical information, characterized in that the sorting part is controlled to prevent microparticles not sorted as belonging to the first microparticle population or second microparticle population from entering the particle sorting flow channel by causing the microparticles not sorted as belonging to the first microparticle population or second microparticle population to flow into one or more branched flow channels branched from the main flow channel. obtain optical information indicating a first microparticle population and a second microparticle population; control, based on light from the microparticles detected by a detection unit in response to irradiating the microparticles with excitation light as the microparticles flow through a main flow channel and based on a predetermined ratio or range of ratios of the first microparticle population and the second microparticle population, a sorting part to perform sorting of a first group of microparticles belonging to the first microparticle population and a second group of microparticles belonging to the second microparticle population to obtain a mixture of microparticles including microparticles both from the first microparticle population and the second microparticle population in a particle sorting flow channel coaxial with the main flow channel according to the predetermined ratio or range of ratios, the first group of microparticles being determined as belonging in the first microparticle population and the second group of microparticles being determined as belonging in the second microparticle population based on at least one characteristic of the detected light and the optical information, characterized in that the sorting part is controlled to prevent microparticles not sorted as belonging to the first microparticle population or second microparticle population from entering the particle sorting flow channel by causing the microparticles not sorted as belonging to the first microparticle population or second microparticle population to flow into one or more branched flow channels branched from the main flow channel. <EOS>