PURPOSE: To produce a porous urethane article having excellent moisture permeability, gas permeability and good waterproofness, by applying a polyurethane resin contg. hydrophobic group-treated hydrated silicic acid powder to a support and immersing the support in water.

CONSTITUTION: 1W30pts.wt. hydrophobic group-treated hydrated silicic acid powder (e.g. hydrated silicic acid obtd. by treating it with dimethyldichlorosilane to thereby allow it to have a DBA value of hydrophobicity of 0) is added to a polyurethane resin soln. (e.g. a dimethylformamide soln. of a polyester polyurethane resin). The resulting polyurethane resin soln. is applied to a support. The support is then immersed in water or a soln. mainly composed of water (e.g. an aq. methanol soln.) to produce a porous urethane article. In the replacement, of the solvent with water or the aq. soln. mainly composed of water, very fine pores are formed on the surface of the support by the action of the hydrophobic group and the replacement rate in the inside is so slow, that deep large voids are formed in the inside. Thus, a porous urethane article having excellent waterproofness and moisture and gas permeability can be obtd.