Disclosed is an auto injector handpiece which can effectively filter foreign substances included in air which is sucked into a main body of an auto injector. The auto injector handpiece comprises: a handpiece housing which encloses a syringe comprising a syringe body and a syringe plunger a piston arranged to push the rear end of the syringe plunger and move the same an actuator actuating the piston forwards a suction needle member which is connected to the front end of the syringe body and has a needle and a concave part formed around the needle an air pipe connecting the concave part of the suction needle member and a vacuum pump and an air filter which is installed on one side of the handpiece housing to be separable, and which filters foreign substances included in air sucked from the concave part on the middle of the air pipe. The air filter comprises: a filter housing which has an inlet connecting part formed on the front of the filter housing and an outlet connecting part formed on the rear of the filter housing a filter medium arranged on the inner rear side of the filter housing in order to remove the foreign substances included in the sucked air which flows into the filter housing through the inlet connecting part and flows out through the outlet connecting part and a foreign substance filtering structure formed on the inner front side of the filter housing to block the foreign substances included in the sucked air and filter out the foreign substances. The foreign substance filtering structure comprises: a lower chamber connected to the inlet connecting part an upper chamber connected to the outlet connecting part a filtering diaphragm partitioning the lower chamber and the upper chamber and a filtering hole formed on the filtering diaphragm.COPYRIGHT KIPO 2016실린지 바디와 실린지 플런저를 포함하는 실린지가 장입되는 핸드피스 하우징 상기 실린지 플런저의 후단을 밀어 이동시키도록 배치되는 피스톤 상기 피스톤을 전방으로 구동시키는 액추에이터 상기 실린지 바디의 전단에 연결되며 바늘 및 상기 바늘 주변의 오목부를 구비하는 석션 니들 부재 상기 석션 니들 부재의 오목부와 진공펌프를 연결하는 에어 관로 및 상기 핸드피
