An actuator for a medical device includes a housing (10), a driving unit (20) mounted in the housing, a first moving unit (30) slidably mounted in the housing and movable by the driving unit. The first moving unit includes a movable first car (32), a spring (70) with two ends thereof abutting the housing (10) and first car (32), respectively, and a lock (40) formed between the driving unit (20) and first car (32). The lock includes a first snap (42) and a first protrusion (45) detachably engagable with the first snap (42). One of the first snap (42) and first protrusion (45) is formed on the first car (32), and the other is formed on the driving unit (20). When the first protrusion (45) disengages from the first snap (42), the spring (70) moves the first car (32) relative to the housing (10).
