Method and apparatus for conditioning weakly to medium-active wastes through fused vitrification by means of electric electrodes for generating the melting heat. The wastes optionally with additive materials are filled into a cup-shaped melting crucible which contains at least two electrodes. The melting crucible is closed off at the top by a furnace hood which has current leads. Voltage is applied to the electrodes via the current leads until the melting crucible containing material to be melted has melted. The current leads are separated from the electrodes. The furnace hood is removed, and after the cooling down, the melting crucible is filled with inactive cement paste to produce a cover layer.