This liquid medicine administration device 100 includes a liquid medicine container 110, a gasket 135 for expelling the liquid medicine in the liquid medicine container, a plunger 130 capable of pressing the gasket, a housing 120, a drive mechanism 140 that advances the plunger, and a rotation restriction unit 150 that restricts rotation of the plunger. The drive mechanism includes a motor 141 and a feed screw 143. The plunger includes: a threaded portion 131 threadedly engaged with the feed screw; and a plunger body 132 that advances with the rotation of the feed screw and that presses the gasket, while the rotation of the plunger with respect to the housing is being restricted by the rotation restriction unit. The plunger is provided with a canceling mechanism that cancels the transmission of a pressing force from the plunger body to the gasket when the plunger body receives an axial reaction force equal to or greater than a preset pressing force from the gasket during advancement with the rotation of the feed screw.
