In order to establish an application method of cavitating field to a chemical reactor, reduction of carbon dioxide was demonstrated using a cavitating jet. The test water was injected into a chamber filled with water dissolved carbon dioxide as a cavitating jet. When the residual bubble after cavitation bubble collapse was analyzed by a gas chromatography, the methane was detected in the residual bubble. In order to clarify the chemical reaction at cavitation bubble collapse, radical induced by the cavitation bubble collapse was evaluated by measuring spectra of luminescence. The radical induced by cavitating flow was also evaluated by an electron spin resonance, comparing the result of cavitation induced by ultrasonic.