A linear actuator (1) having: a shaft (26) that is forward/reverse rotated by a motor via a worm (36) and a worm wheel (41) a screw nut (29) threadably mounted to the shaft (26) and a piston tube (10) fixed to the screw nut (29) and that advances and retreats in accordance with the rotation of the shaft (26). A metal coupling (42) is attached on the inside, in the radial direction, of the worm wheel (41). A one-way clutch (44) is attached on the inside, in the radial direction, of the coupling (42). A brake unit (45) that does not apply braking force during forward rotation, during which the piston tube (10) extends, and does apply braking force during reverse rotation of the piston tube (10) is connected to the one-way clutch (44).線性致動器(1),具有:透過蝸桿(36)及蝸輪(41)由馬達驅動成正轉或反轉的傳動軸(26);螺合安裝在傳動軸(26)的螺帽(29);及固定在螺帽(29)且隨著傳動軸(26)的旋轉而形成進退的活塞管(10)。於蝸輪(41)的徑方向內側安裝有金屬製的聯軸器(42)。於聯軸器(42)的徑方向內側安裝有單向離合器(44)。於單向離合器(44),連接有制動單元(45),該制動單元(45)構成為當活塞管(10)為伸長之正轉動作時並不施以制動力,但當活塞管(10)為反轉動作時就施以制動力。1‧‧‧線性致動器2‧‧‧醫療暨看護床3‧‧‧背底部4‧‧‧框架5‧‧‧本體殼7‧‧‧活塞單元8‧‧‧U形環9‧‧‧致動器支撐軸10‧‧‧活塞管11‧‧‧連桿12‧‧‧連桿連接軸
