The liquid-drug administration device according to the present invention includes an actuator (11), gears (13, 15, 17) driven by the actuator (11), an output shaft (19) provided on the rotation axis of the gear (17) to slide a plunger (103) in a syringe (101) for containing liquid-drug, and an occlusion detector (20) provide between the actuator (11) and the output shaft (19) to detect occlusion in a flow passage for liquid-drug supplied from a syringe (101). The occlusion detector (20) includes a fixed slit disk (21) that has a slit (s1) in its disk face and rotates in synchronization with the rotation of the actuator (11), a slit disk (23) that has a slit (s2) in its disk face and rotates in synchronization with the rotation of the output shaft (19), the slit disk (23) being coaxially and overlappingly assembled to the fixed slit disk (21), and an elastic member (25) that connects the fixed slit disk (21) to the slit disk (23) to cause a delay in rotation of the slit disk (23) with respect to the rotation of the fixed slit disk (21) in response to the rise in the back pressure on the slit disk (23).
