Disclosed herein is an apparatus and a method for producing a pyrolysis liquid, wherein the pyrolysis liquid is formed by means of pyrolysis from a raw material by forming, and a pyrolysis reactor, a gaseous pyrolysis product by pyrolysis and condensing it in a condenser into a pyrolysis liquid, and feeding circulation gas into the pyrolysis reactor. The circulation gas is conducted by a liquid ring compressor into the pyrolysis reactor and purified before being conducted into the pyrolysis reactor, and the pyrolysis liquid is used as the liquid layer in the liquid ring compressor.