A casting motion or a jumping motion can enhance the traverse ability and agility simultaneously of a mobile robot. This paper describes the development of a novel actuator, based on a pneumatic driving unit, which enables the generation of high-speed motion necessary to realize the motions mentioned above. The proposed actuator, named Magnetic Brake (MB) Cylinder, is composed of a pneumatic cylinder, a permanent magnet, a portable tank, and small valves. The speed of conventional pneumatic cylinders highly depends on the size of the valve which drives it. Since the magnet plays a role to enhance the impulsive release function of pneumatic energy instead of using a big and heavy valve, the pressure inside the cylinder can be kept in high condition, enabling the generation of high velocity with light structure. The height control method of casted objects with the MB Cylinder and its design method are also described in this paper. The analysis of the performance of the MB Cylinder and its simulation method are described for when using the MB Cylinder for both casting motion and jumping motion. After the developed unit is installed on both the casting device and the jumping robot, the validity of the proposed methods is experimentally verified in addition to discussion on its application to rescue operation.