Provided are urea manufacturing method and apparatus, which can increase the conversion ratio into urea and to reduce the consumption of steam. The temperature of the reactor is increased by introducing the entire amount of raw material ammonia and introducing a portion of the decomposed gas from the stripper into the reactor. The raw material ammonia is preferably heated using the steam condensate generated in the purification step, and/or the steam generated by the heat of condensation of the decomposed gas and the unreacted substances in the condensation step. The heating temperature is preferably between 70 and 140° C.