This experimental study investigated how changes in the water flow rate affected the number and size of microbubbles using venturi with equal entry and exit angles of 30°. The water flow rate ranged between 10 and 18 . Photos of microbubbles were taken with a digital camera in a visualized section that was specifically installed to store a certain amount of water to measure microbubble size and the number of microbubbles. The experimental results indicated that when the water flow rate increased, the airflow rate also increased. The microbubble size tended to decrease when the water flow rate increased; the sizes obtained were in the range of 50–130. The amount of air bubbles tended to increase when the water flow rate increased.