A rocket propulsion device including, a case having a propellant therein, the case in the form of a tube, a nozzle having at least part inserted in the case, and configured to discharge gas upon burning the propellant, and a locking unit disposed to be wound on the nozzle, the locking unit in the form of a band having both ends open, wherein a through hole for inserting the locking unit therein is formed at one region on a circumference of the case, and the both ends of the locking unit are located at a region facing the one region, whereby a rocket propulsion device having a simplified structure and a facilitated alignment of a thrust line can be implemented.