The present invention is directed to a technique which comprises the steps of stopping the rotation of a treating drum in a deodorizing step, introducing the outside air into a treating tank through an upper opening provided in the upper portion of the treating tank or the upper portion of a recovery air duct, simultaneously exhausting a solvent gas from the treating tank through a lower opening provided in the lower portion of the treating tank or a button trap portion so slowly as not to agitate the solvent gas in the treating tank by an exhaust means connected to a solvent recovery device in the condition that the treating drum is stopped, in order to replace the solvent gas in the treating tank with the outside air, and reusing the solvent gas through the solvent recovery device once or several times. In addition, the present invention is further directed to an improvement of the above-mentioned technique. According to the above-mentioned technique of the present invention, a gas throughput which is required to recover a certain amount of the solvent in the treating tank can be noticeably miniaturized and hence it can be manufactured at a lower cost, as compared with conventional ones, and air pollution and the breakage of ozone layer can be prevented. Moreover, the solvent can be saved owing to its recovery and reuse, and occupation space for the solvent recovery device can be also saved.