A method of producing a polyurethane-based composite material, comprising: a polyaddition reaction step of subjecting a diol compound having one or more radically polymerizable groups and a diisocyanate compound to a polyaddition reaction in a polyaddition-reactive raw material composition containing the diol compound, the diisocyanate compound, and a polymerizable monomer having one or more radically polymerizable groups in a molecule, and being free from causing a polyaddition reaction with any of the diol compound and the diisocyanate compound, to thereby form a polyurethane component having a number average molecular weight of from 1,500 to 5,000, measured as disclosed in the description and having a radically polymerizable group; a radically polymerizable raw material composition-preparing step of preparing a radically polymerizable raw material composition containing the polyurethane component, the polymerizable monomer, a radical polymerization initiator, and a filler; and a radical polymerization step of performing radical polymerization using the radically polymerizable raw material composition after completion of the polyaddition reaction step and the radically polymerizable raw material composition-preparing step, to thereby form a polyurethane-based composite material, wherein a polymerizable monomer blending ratio Rr represented by the following equation is from 20 mass% to 80 mass%: · Rr = 100 × Br / a 1 r + a 2 r + Ar + Br in the equation, a1r represents a content (parts by mass) of the diol compound remaining unreacted in the radically polymerizable raw material composition, a2r represents a content (parts by mass) of the diisocyanate compound remaining unreacted in the radically polymerizable raw material composition, Ar represents a content (parts by mass) of the polyurethane component in the radically polymerizable raw material composition, and Br represents a content (parts by mass) of the polymerizable monomer in the radically polymerizable raw material composition. a polyaddition reaction step of subjecting a diol compound having one or more radically polymerizable groups and a diisocyanate compound to a polyaddition reaction in a polyaddition-reactive raw material composition containing the diol compound, the diisocyanate compound, and a polymerizable monomer having one or more radically polymerizable groups in a molecule, and being free from causing a polyaddition reaction with any of the diol compound and the diisocyanate compound, to thereby form a polyurethane component having a number average molecular weight of from 1,500 to 5,000, measured as disclosed in the description and having a radically polymerizable group; a radically polymerizable raw material composition-preparing step of preparing a radically polymerizable raw material composition containing the polyurethane component, the polymerizable monomer, a radical polymerization initiator, and a filler; and a radical polymerization step of performing radical polymerization using the radically polymerizable raw material composition after completion of the polyaddition reaction step and the radically polymerizable raw material composition-preparing step, to thereby form a polyurethane-based composite material, wherein a polymerizable monomer blending ratio Rr represented by the following equation is from 20 mass% to 80 mass%: · Rr = 100 × Br / a 1 r + a 2 r + Ar + Br · Rr = 100 × Br / a 1 r + a 2 r + Ar + Br