Provided is a fly wheel, including: a fly wheel body provided with a receiving part in which air is filled and mounted on driving shaft; a blade radially coupled to the fly wheel body, including a ventilation passage formed therein to be communicated with the receiving part and a puncturing part formed on an outer race thereof to be communicated with the ventilation passage, and generating thrust by discharging the air filled in the receiving part to the puncturing part at the time of rotating the driving shaft; and a check valve installed on the fly wheel body and being opened and closed by a pressure difference between the receiving part and the outside.