Provided is a syringe drive unit (1) which is capable of imparting a fine moving amount to a plunger pressing member (6) when a plunger is pushed into a syringe body using a feed screw mechanism, to thereby eject liquid medicine from the syringe body with high accuracy. The syringe drive unit (1) includes: a syringe holder (3) which is fixed to a front surface side of a base plate (2) and holds the syringe body a guide rail (4) which is provided on a rear surface side of the base plate (2) along an axial-line direction of the syringe body a slider (5) which is assembled to the guide rail (4) through intermediation of rolling elements a plunger pressing member (6) which is fixed to the slider (5) and includes an arm portion (61) projecting from the rear surface side of the base plate (2) to the front surface side of the base plate (2), the arm portion (61) holding the plunger housed in the syringe body a screw shaft (7) which is provided parallel to the guide rail (4) and has predetermined rotation imparted by a motor (9) and a nut member (8) for imparting a moving amount corresponding to a rotation amount of the screw shaft (7) to the plunger pressing member (6).
