A power actuator based on a great volume expansion on hydrogenation of hydrogen storage alloys (HSAs) has been developed. The actuator has a bimorph structure consisting of Pd-Ni alloy and Cu-plating to convert the volume change into bending motion. The techniques to control the bending and rotation motions of the actuator were investigated by adjusting alloy composition, shape and the amount of hydrogen absorbed in the HSA. It is found that Pd-Ni alloy actuators exhibit a cyclic bending motion on hydrogen absorption and desorption cycles and the bending behavior can be controlled by controlling the hydrogen pressure. When a ribbon shaped actuator was deformed into the “L” shape on the transverse section, a rotation motion was observed without modifying the basic bimorph structure of the actuator.