In order to improve the traveling performance of robotic system in the fields with rough terrains and uncertainties, the hopping mechanism is sometimes employed as a locomotion method. In our preceding study, a hopping mechanism utilizing the energy generated by resonance is proposed, and we revealed that simple resonance of the system resulted in insufficient hopping height and that some additional devices were required to obtain a meaningful hopping height of the system. In this paper, a hopping mechanism with stiffness switching is proposed to achieve a meaningful hopping height. The stiffness is switched by an electrical method through the use of piezoelectric elements and capacitors connected to it. It is expected that the proposed mechanism leads to a realization of a smaller and more reliable hopping mechanism since it has quite simple configuration. The proposed mechanism is analyzed theoretically and the effectiveness of the mechanism is confirmed by numerical analyses.