The invention discloses a nano bubble generator. The nano bubble generator comprises a shell, a horizontal partition plate, a filter plate and microflow tubes; the microflow tubes comprise an inner tube, an outer tube and a copper foil roll arranged between the inner tube and the outer tube, and the copper foil roll is prepared from a copper foil of which the surface is provided with micro air flow groove channels in an etching mode; and the nano bubble generator further comprises an air pump used for injecting air into an air cavity and a water pump used for injecting water into an air-liquidmixing cavity. According to the nano bubble generator, the copper foil which is provided with a large quantity of micro air flow groove channels in the etching mode is rolled to form the microflow tubes, high-pressure air generates a large quantity of micro air flows through the microflow tubes, the micro air flows are sheared by a blade rotating at high speed, and then a large quantity of nano bubbles are formed in the air-liquid mixing cavity. According to the nano bubble generator, the size of the nano bubbles generated by the nano bubble generator can be controlled by controlling the diameter of the micro air flow groove channels and the rotation speed of a motor, the generated nano bubbles are stable in size and large in bubble quantity, the flotation efficiency can be improved, andthe mineral recovery rate can be increased.