Inhyuk,
I see two things here: first, you are not finishing your jump. You need to get hips / knees fully extended, and let the jump carry you off the ground. You're picking your feet up and stomping them instead of allowing full extension to carry you off the ground. Make sense?
The second thing I see is that you are not waiting long enough to jump. Jump a bit higher on the thigh, and finish your jump, and you'll stop moving forward each time. It may help to think about jumping back.