Method of manufacturing polishing pad

A method of manufacturing a polishing pad, the method comprising:

• (a) producing an urethane prepolymer having a viscosity of 20,000 cps (at 25° C.) to 40,000 cps (at 25° C.) by mixing a plurality of polymer molecules, wherein the plurality of polymer molecules comprises a polymer having four or more hydroxyl groups, and an amount of the polymer having four or more hydroxyl groups ranges from 1% to 30% based on a total weight of the urethane prepolymer;
• (b) mixing the urethane prepolymer produced at the producing step (a) with an inert gas and a low-boiling blowing agent having a boiling point of 60° C. to 150° C.;
• and
• (c) manufacturing a polishing layer including porous pores by causing a mixture produced at the mixing step (b) to be subjected to gelation and curing in a predetermined cast,
• wherein, the mixing step (b) includes causing an average size of pores produced by mixing the inert gas of 5% to 30% and the low-boiling blowing agent of 0.1% to 10% of a total volume of a mixture produced at the mixing step (b) with the urethane prepolymer produced at the producing step (a) to be 31 μm or smaller.