A process is provided herein for obtaining a high purity nitrogen trifluoride gas containing at least oxygen difluoride which is used as a dry etching agent for semiconductors or a cleaning gas for CVD apparatus, etc. The process comprises removing hydrogen fluoride to 100 ppm or less in the nitrogen trifluoride gas and then contacting the nitrogen trifluoride gas with at least one aqueous solution containing a component selected from the group consisting of sodium thiosulfate, hydrogen iodide and sodium sulfide to remove oxygen difluoride.
