A method for producing an isocyanate, comprising: a carbamation step of generating an N-substituted carbamate from an organic primary amine, urea and an organic hydroxy compound according to a carbamation reaction, and then recovering a first gaseous phase component containing the urea and/or a compound having a carbonyl group derived from the urea, the organic hydroxy compound, and ammonia; a condensation step of condensing the first gaseous phase component with a condenser; an isocyanate production step of producing an isocyanate by subjecting the N-substituted carbamate to pyrolysis; an ammonia absorption step of allowing a second gaseous phase component containing ammonia recovered as a gaseous phase component from the condenseras a main component, to be absorbed by absorption water, and generating gas-absorbed water; and an ammonia stripping step of heating the gas-absorbed water to separate ammonia from the gas-absorbed water.