PURPOSE: To prepare a porous sheet useful for simulated synthetic leather substitute, preventing water penetration without damaging permeability and water vapor transmission, by adding an urethane oligomer containing a specific perfluoroalkyl group to a solution of a polyurethane elastomer-containing resin.

CONSTITUTION: A solution of a resin comprising polyurethane elastomer as an essential component is blended with 1W10wt% based on the elastomer of urethane oligomer [e.g., compound shown by the formula Rf-X-OH (Rf is 6W12C perfluoroalkyl; X is 1W6C alkylene, arylene, etc.] containing a perfluoroalkyl group having compatibility with the elastomer or miscibility with the solvent for the resin, the solution with the solvent is applied to a substrate, or impregnated into it, the substrate is treated with a liquid substance and/or its vapor having affinity for the solvent but not for the elastomer, to prepare a porous sheet material.