A method and a device using pyrolysis for recycling used printed circuit board in which water (moisture) is introduced in the pyrolysis process and a fully sealed low pressure environment is established to ensure that no combustion happens in the pyrolysis process to enhance the safety of the process; pyrolysis gases generated in the process are concentrated and purified to provide useful fuels or chemical materials; therefore, the present invention can reduce process cost, improve recycling efficiency and provide processing device with high safety, thereby enhancing industry usability.