Help please! Is ab crunch machine good to lose belly fat?

Any. Any form of exercise that burns up calories will help you lose weight if combined with a calorie restricted diet. Avoid fat and junk food. See a registered dietitian for help. It takes 3500 calories to burn up one pound that you don't eat. Good luck. Your body will determine where it wants to burn up the fat. All you can do is tone up the muscles under the fat.
Spot fat loss does . Not occur naturally. By losing weight in general some will probably be abdominal fat. But, we don't get to choose what area of body fat is lost from. Eat healthy ; be physically active. Calories burned must > those consumed. Tighten ab's: crunches, reverse crunches, exercise ball crunches, pelvic thrusts, lying leg raises, side bridge ; “bicycling” exercise on back. Do regular aerobic exercise.