Fleas can jump more than 200 times their body length. They do so by employing a unique catapult mechanism: storing a large amount of elastic energy and releasing it quickly by torque reversal triggering. This paper presents a flea-inspired catapult mechanism for miniature jumping robots. A robotic design was created to realize the mechanism for the biological catapult with shape memory alloy (SMA) spring actuators and a smart composite microstructure. SMA spring actuators replace conventional actuators, transmissions, and the elastic element to reduce the size. The body uses a four-bar mechanism that simulates a flea's leg kinematics with reduced degrees of freedom. Dynamic modeling was derived, and theoretical jumping was simulated to optimize the leg design for increased takeoff speed. A robotic prototype was fabricated with 1.1-g weight and 2-cm body size that can jump a distance of up to 30 times its body size.