To provide a gas/liquid mixing apparatus capable of effectively generating gas bubbles, and a water purifier equipped with it.

The gas/liquid mixing apparatus 110 includes a fine air bubble generator 32 having a negative pressure part and a housing 10. The negative-pressure part of the fine air bubble generator 32 puts water into circulation, sucks a gas by changing it to a negative-pressure state, and dissolves the sucked gas in water, thus generating microscopic air bubbles in water. The housing 10 has an inflow port 41 and an outflow port 51. The inflow port 41 causes water, having microscopic air bubbles and flowed through the fine air bubble generator 32, to flow into the housing 10. The outflow port 51 causes water, flowing from the inflow port 41 and having fine air bubbles, to outflow from the housing 10. The aperture of the outflow port 51 is larger than the aperture of the inflow port 41.