A microrobotic leg actuated with amplifying mechanisms is developed in this paper to mimic the motion of legs in natural organisms on the small scale. The leg device has a planar structure and is fabricated with bulk micromachining. Two electrothermal actuators are used to drive the leg back and forth in the planar workspace. The actuator motion is transmitted elastically to the leg using flexible arms. The leg mechanism has a symmetrical structure similar to standard parallel planar manipulators but with deformable parts instead of joints. The motion of the leg at the tip side is further amplified by blocking its motion at the other side using stoppers, resulting in an extended range of motion at the leg tip. Finite element simulations and experimental tests on fabricated prototypes demonstrated the efficient operation of the proposed design. The unique characteristics of the proposed leg mechanism, including large force and displacement, multiple degrees of freedom, and compatibility with micromachining, enhance the power, control, and mobility autonomy of legged microbots.