A method of producing a polyurethane-based composite material, comprising: a polyaddition reaction step of subjecting a diol compound (a1) having one or more radically polymerizable groups and a diisocyanate compound (a2) to a polyaddition reaction in a polyaddition-reactive raw material composition containing the diol compound (a1), the diisocyanate compound (a2), and a polymerizable monomer (B) having one or more radically polymerizable groups in a molecule, and being free from causing a polyaddition reaction with any of the diol compound (a1) and the diisocyanate compound (a2), to thereby form a polyurethane component (A) 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 (A), the polymerizable monomer (B), a radical polymerization initiator (C), and a filler (D); 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 (a1) remaining unreacted in the radically polymerizable raw material composition, a2r represents a content (parts by mass) of the diisocyanate compound (a2) remaining unreacted in the radically polymerizable raw material composition, Ar represents a content (parts by mass) of the polyurethane component (A) in the radically polymerizable raw material composition, and Br represents a content (parts by mass) of the polymerizable monomer (B) in the radically polymerizable raw material composition. a polyaddition reaction step of subjecting a diol compound (a1) having one or more radically polymerizable groups and a diisocyanate compound (a2) to a polyaddition reaction in a polyaddition-reactive raw material composition containing the diol compound (a1), the diisocyanate compound (a2), and a polymerizable monomer (B) having one or more radically polymerizable groups in a molecule, and being free from causing a polyaddition reaction with any of the diol compound (a1) and the diisocyanate compound (a2), to thereby form a polyurethane component (A) 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 (A), the polymerizable monomer (B), a radical polymerization initiator (C), and a filler (D); 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 <EOS>