The present invention discloses a liquid medicine injection device that is attached to a patient's body to inject liquid medicine such as insulin at an appropriate time.A liquid medicine injection device according to the present invention includes: a case; a liquid medicine tank that is disposed in the case and where liquid medicine is received; an electro-osmosis pump that is connected with the liquid medicine tank and moves the liquid medicine; a needle assembly that receives the liquid medicine by being connected to the electro-osmosis pump and injects the received liquid medicine into a human body; and an adhesive member combined to the case and attached to the human body.