I want to lose my belly fat and I wanna know if ab crunch machine is an effective way of doing so?

No. You can not spot train to loose belly fat, you have to loose it all over. Cardio workout 4-5x/wk mixed with 1-2 days of strength training ( including crunches) is the best way to loose weight and tone up.
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. The ab crunch machine may tone abs' but won't remove the fat.