The application device for liquid containing micro-nano bubbles generates micro-nano bubbles in a wide size distribution with use of a submerged pump-type micro-nano bubble generator and a spiral flow-type micro-nano bubble generator. A micro-nano bubble generating aid metering pump is controlled by a bubble level meter and a level controller, so that the supply amount of a micro-nano bubble generating aid is controlled in response to the level of bubbles from a fluid level. The supply amount of a micro-nano bubble generating aid is also controlled by a turbidimeter and a controller in response to the turbidity of the liquid in a micro-nano bubble generation tank, while the amount of air supplied to the submerged pump-type micro-nano bubble generator is controlled in response to the turbidity of the liquid. Therefore, the device can produce a large amount of various micro-nano bubbles in a wide size distribution more economically.