Abstract: A braking device of a three wheel baby car is disclosed. When a moving baby car is desired to be braked, the user only needs to move the protrusion of the braking device between the two rear wheel so as to drive the ejecting notches on the edge of long axis of a rotary portion within the braking device to engage with the inner ends of braking ejecting rods on the two sides. Thus, the original long axis contact with the inner end of the braking ejecting rod is changed as short axis contact. As a result, the braking rods on the two sides will be pushed outwards so that the two ends of the braking ejecting rod directly runs across the respect groove formed on the rear wheels. Accordingly, by this braking device, the baby car will be braked steadily.