A process for producing polyhydroxyurethane microparticles, which are spherical polymer microparticles having particle sizes of 0.1 μm to 300 μm, a polymer that makes up the polymer microparticles has in a structure thereof at least one of two types of chemical structure units represented by the following formulas and, and -O-CO- bonds that make up the chemical structure units, respectively, have been derived from carbon dioxide; said process comprising: upon obtaining the polymer microparticles in a form of being dispersed in an inert liquid by using a compound, which has at least two 5-membered cyclic carbonate groups as reactive groups, and a compound, which has at least two amino groups as reactive groups, homogeneously dispersing these compounds in the inert liquid with a dispersant contained therein, and then heating the resulting dispersion to react both the compounds, wherein neither the cyclic carbonate compound and amine compounds as reactants nor the hydroxyurethane resin available from the reaction of both of them are soluble at all in the inert liquid, using, as one of the compounds, a compound having at least three reactive groups in a molecule, and reacting both the compounds at an equivalent ratio of functional groups, as defined by the following equation, of 0.7 to 1.5. Equivalent ratio of functional groups = mass of the carbonate compound in a composition × number of functional groups in the carbonate compound ÷ molecular weight of the carbonate compound / mass of the amine compound in the composition × number of functional groups in the amine compound ÷ molecular weight of the amine compound wherein the number of functional groups in the carbonate compound means the number of cyclic carbonate structures which the carbonate compound has in a molecule thereof, and the number of functional groups in the amine compound means the number of amino groups which the amine compound has in a molecule thereof. upon obtaining the polymer microparticles in a form of being dispersed in an inert liquid by using a compound, which has at least two 5-membered cyclic carbonate groups as reactive groups, and a compound, which has at least two amino groups as reactive groups, homogeneously dispersing these compounds in the inert liquid with a dispersant contained therein, and then heating the resulting dispersion to react both the compounds, wherein neither the cyclic carbonate compound and amine compounds as reactants nor the hydroxyurethane resin available from the reaction of both of them are soluble at all in the inert liquid, using, as one of the compounds, a compound having at least three reactive groups in a molecule, and reacting both the compounds at an equivalent ratio of functional groups, as defined by the following equation, of 0.7 to 1.5. Equivalent ratio of functional groups = mass of the carbonate compound in a composition × number of functional groups in the carbonate compound ÷ molecular weight of the carbonate compound / mass of the amine compound in the composition × number of functional groups in the amine compound ÷ molecular weight of the amine compound wherein the number of functional groups in the carbonate compound means the number of cyclic carbonate structures which the carbonate compound has in a molecule thereof, and the number of functional groups in the amine compound means the number of amino groups which the amine compound has in a molecule thereof.