A bubble generating apparatus includes a hollow shell having a plurality of bottom inlets through and a side outlet, a screw rod longitudinally mounted in the shell, a baffle threaded onto one end of the screw rod and suspended inside the shell above the bottom inlets, the baffle having a plurality of smoothly arched bottom notches for baffling intake flows of high pressure liquid to produce bubbles, and a knob fastened to one end of the screw rod outside the shell and rotated to move the baffle along the screw rod relative to the bottom inlets.