Disclosed is a chemical solution administration device and a control method for the chemical solution administration device that can prevent an extrusion mechanism such as a plunger for extruding a chemical solution from moving easily with respect to a housing portion such as a cylinder. When a predetermined time has elapsed since a chemical liquid administration apparatus 100 according to the present invention has commanded a motor 136 to stop operation, a processing unit 134a of a first control unit 134 moves an extrusion mechanism 143 to move the chemical liquid. The drive mechanism 131 is commanded to change the position of the sealing member 149 relative to the storage space of the storage unit 141. [Selection] Figure 9【課題】薬液を押し出すプランジャなどの押出機構が筒体などの収容部に対して移動しづらくなることを防止できる薬液投与装置および薬液投与装置の制御方法を提供する。【解決手段】本発明に係る薬液投与装置１００は、モータ１３６に動作の停止を命令してから所定時間経過した場合、第１制御部１３４の処理部１３４ａは、押出機構１４３を移動させて薬液貯蔵部１４１の収容空間に対する封止部材１４９の位置を変化させるように駆動機構１３１に動作を命令する。【選択図】図９
