Waste gas/wastewater treatment equipment treats waste gas in a scrubber 18 by using micronanobubble water produced in a micronanobubble reaction vessel 31 as washing water. Waste gas is efficiently cleaned by the substance surface high-velocity cleaning function which micronanobubbles have. The washing water having been used in the waste gas treatment is reused in wastewater treatment in adjustment tank 1, denitrification tank 3 and nitrification tank 11 which constitute a wastewater treatment section. Thus, the micronanobubbles contained in the washing water are utilized in wastewater treatment, so that efficiency of wastewater treatment is enhanced.