The purpose of this invention is to provide a linear dental cartridge electric syringe that can attain the forward drive of a push rod by arranging the drive shaft of the motor with a reducing gear(reduction motor), serving as a prime drive, and the push rod in a straight line and by using a simple mechanism. This linear dental cartridge electric syringe includes a push rod (32) that has male thread and is arranged with the driving shaft having a reducing gear (reduction motor) (28) in a straight line to non-rotatably move along the axial direction a rotary tube (40) rotated by the drive shaft a screw nut (57) formed by a pair of arm-shape nut halves (56) that are arranged opposing to each other to pivotedlly attach to the rotary tube and have the female threads (68) to mesh with the male threads (34) of the push rod (32) a locking ring (70) arranged between the rear position where the female threads of arm-shape nut half mesh with the male threads of the push rod and the front position where the meshing is released so as to rotate and move along the axial direction a pusher pin (75) inserted into cylindrical space (24) and pressed by the end of a cartridge holder (22) connecting to the cyclindrical space (24) so as to move the lock ring (70) from the front position to near position and a coil spring (80) to push the lock ring (70) back to the position when the cartridge holder (22) is not inserted into the cylindrical space. Thereby, the rotation of the rotary tube (40) makes the screw nut (57) rotate around the push rod (32), and the thread action makes the push rod (32) move forwards.本發明的目的是提供一種:藉由將作為發動機之附有減速機的馬達(減速馬達)的驅動軸與推桿配置在一直線上,並能以簡單的機構達成推桿之前進驅動的線形牙科用電動注射裝置。線形牙科用電動注射裝置包含:具有公螺紋的推桿(32),該具有公螺紋的推桿(32)與附有減速機的馬達(減速馬達)(28)的驅動軸形成一直線,並配置成可非旋轉地移動於長軸方向上;和旋轉筒(40),該旋轉筒(40)是藉由驅動軸而旋轉;和螺帽(57),該螺帽(57)是由一對彼此相對向的臂狀螺帽半部(56)所形成,該一對彼此相對向的臂狀螺帽半部(56)是旋轉附著於旋轉筒,並具有與前述推桿(32)的公螺紋(34)嚙合的母螺紋(68);和鎖環(70),該鎖環(70)被配置成可在「使臂狀螺帽半部之母螺紋與前述推桿之公螺紋嚙合」的後方位置、及用來解放該嚙合的前方位置之間,移動於長軸方向上並且可以旋轉;和襯套銷(75),該襯
