Abstract: A compact organic solvent recovery system includes a backup treatment apparatus for environmentally safe treatment of an organic solvent leaking into a gas exiting an adsorption tower packed with an adsorbing material such as particulate active charcoal or active carbon fiber. Adsorption treatment of organic solvents includes introducing an organic solvent containing gas to be treated into an organic solvent recovery apparatus including an adsorption tower packed with adsorbing material. By subsequently introducing steam into the adsorption tower, the organic solvents are desorbed. By introducing the treated gas discharged from the organic solvent recovery apparatus into the backup treatment apparatus, the organic solvents leaking into the treated gas are adsorbed, and the gas treated in the backup treatment apparatus is simultaneously discharged as purified gas.