PURPOSE: To reduce the total energy required by utilizing the potential waste heat of a crude synthesis gas in a urea producing process when NH3 is synthesized from carbon-contg. raw material and urea is synthesized using CO2 from the crude synthesis gas and NH3.

CONSTITUTION: In a combined process for producing a crude synthesis gas contg. H2, CO, CO2, etc. by steam reforming or partial oxidation of carbon-contg. raw material; synthesizing NH3 from H2 obtd. by purification of the crude gas and N2; and synthesizing urea from CO2 removed in the purification and NH3, the CO2 is removed by physical absorption, and the crude gas is subjected to indirect heat exchange through no heat medium between a CO converting process and the CO2 removing process. The waste heat generated is utilized as a heat source in the urea synthesizing process. When this urea process is out of operation or in an unstationary state, the crude gas is fed to other waste recovering or cooling process. Thus, ammonia and urea are produced combinedly.