To expect safety in the insolubilization treatment of a harmful substance contained in back-filling polluted soil.

The driving of the supply part conveyor in the supply means S arranged on a base stand B to receive polluted soil and that of the treatment part conveyor 4 in the treatment means D arranged on the base stand B in the same way to subject the polluted soil from the supply means S to insolubilization treatment are stopped when the emergency stop buttons S1, S2 and S3 arranged on the base stand B at a plurality of places in the same way are in their ON-operations.