PURPOSE: To produce a polyurethane elastomer excellent in wet heat resistance and moldability by using a high-mol.-wt. active hydrogen compd. contg. a specific polyoxyalkylene polyol.

CONSTITUTION: In producing a microcellular polyurethane elastomer by using at least two components, i.e., an active hydrogen component contg. a high-mol.- wt. active hydrogen compd., water, and a chain extender as the essential ingredient and an isocyanate component contg. a polyisocyanate compd. as the essential ingredient, a polyoxyalkylene polyol produced by using cesium or a cesium compd. as the catalyst is used at least as a part of the high-mol.-wt. active hydrogen compd. A polyol or an amine is used as the chain extender. The amt. of water used is 0.1-5wt.% of the sum of the high-mol.-wt. active hydrogen compd. and the chain extender.