This paper proposes a piezoelectric actuator based on the parasitic motion principle which overcomes the disadvantage that piezoelectric actuators designed by the parasitic motion principle always sacrifice reverse directional performance for improving forward directional performance. The parasitic motion principle based piezoelectric actuator can use two flexible mechanisms to achieve bidirectional motion, but more assembly errors will be introduced. Therefore, the proposed actuator is designed to output bidirectional motion through one flexible mechanism. To this end, two mounting slots with high flexibility are specially designed for improving output displacement. The working principle and design process are elaborated, and experiments are conducted to prove the feasibility of the proposed actuator. The fabricated prototype can achieve a maximum velocity of 1.563 mm/s and 1.054 mm/s, a displacement resolution of 5.8 µm and 6 µm, an operating bandwidth of 1600 Hz and 1200 Hz, and a vertical load capacity larger than 500 g in forward and reverse directions.