PURPOSE: To provide the title apparatus of easy workability, ensured to cause no contaminative pollution, so designed that ozonized water is spread underground through a jetting port provided on a claw from an ozonized water feeder loaded on the rear of a power tiller.

CONSTITUTION: (A) Ozone produced from an ozonizer 2 loaded on the rear of a power tiller 1 and (B) water from a water tank 3 are mixed in a mixer 5 via pipes 4a, 4b, and the resultant ozonized water is fed into a pipe 4. And a claw 8 fitted on the working machine-fitting part 6 of the tiller is inserted underground 7 and said tiller 1 is made to proceed at reduced speed: at the same time, the above ozonized water is fed via a feed header 12 and a jetting tube 11 to a jetting port 10 formed on the claw 8, being blown underground 7 to accomplish sterilization.