To provide a polyurethane foam having a continuous cell structure, wherein hardness can be adjusted and alterations of physical properties other than hardness are inhibited.

The polyurethane foam having the continuous cell structure is obtained by compounding an aqueous solution prepared by dissolving a hydrogencarbonate in water with a polyurethane foam material containing polyols, polyisocyanates, a foaming agent and a catalyst and reacting, expanding and curing the polyurethane foam material. The hydrogencarbonate is preferably an alkali metal hydrogencarbonate such as sodium hydrogencarbonate and potassium hydrogencarbonate. The decomposition of the hydrogencarbonate preferably starts at 50-100°C. The amount of the hydrogencarbonate compounded is preferably 0.005-0.5 pts.mass per 100 pts.mass. polyols.