The invention relates to a facility for treating composite material containing metal as treating material, comprising a metal separator (22, 22a, 28) mounted upstream of an impact crushing mill (30, 50) -- and optionally an eddy current separator (54) mounted downstream of the impact crushing mill (30, 50) as device for separating the treating material by swirling. In order to recover ferrous and non-ferrous metals from the slag of a garbage incinerating plant, a sieve station (20) is provided, its discharge (21) for fine grain and its discharge (26) for oversize particles being respectively connected to a metal separator (22, 28) and an impact crushing mill (50, 30) being mounted downstream of the discharges (24, 29) for non-magnetic material of said separator. Moreover, a separating cut in the input sieve station that is configured as a scalping screen (20) is provided for oversize grains of approximately 45 mm to approximately 100 mm. A preliminary sieve (12) for grains larger than approximately 100 mm is mounted upstream of the input sifting station (20). A vertical impact crushing mill (30) for oversize grains is connected to the discharge (29) for non-magnetic muck of the metal separator (28), a metal separator (22a) being located at the discharges (31) of said impact crushing mill.