To provide a method for recycling a foamed polystyrene resin by which the foamed polystyrene resin can be recycled without causing deterioration by heat and an apparatus for recycling treatment used for practicing the method for recycling.

A molded product of the foamed polystyrene such as a tray for foods is charged into a volume reducing solvent to provide a viscous material, which is then charged into a separator 2 while being stirred. Steam is added from an addition means 23 to the separator 2 to evaporate and separate the volume reducing agent and water from the viscous material at a lower temperature than that of the volume reducing agent by an azeotropic phenomenon. During the process, the viscous material is cut with a finely dividing means 22 such as a cutter in the separator 2. The volume reducing agent and water are respectively recovered from the mixed evaporated material of the evaporated and separated volume reducing agent and water and reutilized for recycling treatment.