Ultra-high pressure underwater shock wave was applied to sterilize microbe. The imploding detonation of a propane-oxygen mixture was used to generate underwater shock wave in a steel pipe. We investigated imploding detonation waves in an approximately cone-shaped combustion chamber having a maximum inner diameter of 60 mm. As an object of the sterilization experiments, daphnias were used. The experimental results show that maximum pressure at the implosion center was 250 to 400 times higher than the initial pressure, and maximum pressure in the sterilization pipe was 48 to 60 % of the maximum pressure at the implosion center. We found that we could completely sterilize the daphnias by four times treatments of the underwater shock wave that maximum pressure was about 100 MPa.