To detect a bridge in a thermal decomposition waste discharge apparatus easily without fail and to break the detected bridge quickly.

The first pressure detector Pa is installed at the exit of a thermal decomposition residue of a discharge apparatus 11 in a waste treatment apparatus 1, and the second pressure detector Pb, at a position above the discharge apparatus 11 and where the thermal decomposition residue does not stay. The pressure difference between the first detector Pa and the second detector Pb is detected by blowing a nitrogen gas G4 to the vicinity of the first detector Pa. By the pressure difference detection, whether a bridge in the thermal decomposition residue occurs between the two detectors or not is detected. When the occurrence of the bridge is detected, a magnet-type hammer 17 is operated to break the bridge.