A pharmaceutical injection device, comprising: a main body case that has an opening through which an injection needle is inserted and retracted; a pharmaceutical syringe mounting component that is provided inside the main body case and onto which a pharmaceutical syringe is mounted; a piston that is provided movably with respect to the pharmaceutical syringe mounted onto the pharmaceutical syringe mounting component; a drive mechanism that drives the piston; a display component that displays information related to the injection of a pharmaceutical; a memory that is provided inside the main body case and stores a preset pharmaceutical injection schedule; and a controller that is electrically connected to the drive mechanism, the display component, and the memory, and resets a current pharmaceutical dose automatically if there is a difference by comparing a planned cumulative pharmaceutical dose, which is a planned cumulative amount of pharmaceutical injected up to the last time on the basis of the pharmaceutical injection schedule stored in the memory, with an actual cumulative pharmaceutical dose, which is a cumulative amount of pharmaceutical actually injected up to the last time; wherein when the controller determines that the actual cumulative pharmaceutical dose is short of the planned cumulative amount of pharmaceutical dose, the controller resets a current or future pharmaceutical dose greater than a planned amount of pharmaceutical injected on the basis of the pharmaceutical injection schedule so as to compensate the shortage, and when the controller determines the actual cumulative pharmaceutical dose is in excess of the planned cumulative amount of pharmaceutical dose, the controller resets a current or future pharmaceutical dose less than a planned amount of pharmaceutical injected on the basis of the pharmaceutical injection schedule so as to reduce the excess amount. a main body case that has an opening through which an injection needle is inserted and retracted; a pharmaceutical syringe mounting component that is provided inside the main body case and onto which a pharmaceutical syringe is mounted; a piston that is provided movably with respect to the pharmaceutical syringe mounted onto the pharmaceutical syringe mounting component; a drive mechanism that drives the piston; a display component that displays information related to the injection of a pharmaceutical; a memory that is provided inside the main body case and stores a preset pharmaceutical injection schedule; and a controller that is electrically connected to the drive mechanism, the display component, and the memory, and resets a current pharmaceutical dose automatically if there is a difference by comparing a planned cumulative pharmaceutical dose, which is a planned cumulative amount of pharmaceutical injected up to the last time on the basis of the pharmaceutical injection schedule stored in the memory, with an actual cumulative pharmaceutical dose, which is a cumulative amount of pharmaceutical actually injected up to the last time; wherein when the controller determines that the actual cumulative pharmaceutical dose is short of the planned cumulative amount of pharmaceutical dose, the controller resets a current or future pharmaceutical dose greater than a planned amount of pharmaceutical injected on the basis of the pharmaceutical injection schedule so as to compensate the shortage, and when the controller determines the actual cumulative pharmaceutical dose is in excess of the planned cumulative amount of pharmaceutical dose, the controller resets a current or future pharmaceutical dose less than a planned amount of pharmaceutical injected on the basis of the pharmaceutical injection schedule so as to reduce the excess amount.