A pharmaceutical injection device, comprising: a main body case having a pharmaceutical syringe attachment component on its distal end side; the pharmaceutical syringe attachment component having an inner case in which a pharmaceutical syringe unit is attached; a distal end cap that can be removably attached to the distal end side of the main body case; a needle unit having an injection needle, wherein during needle insertion the injection needle protrudes to the distal end side through an opening at the distal end of the distal end cap and pierces the skin; a first driver that is configured to move in a normal pharmaceutical injection mode the pharmaceutical syringe unit attached to the pharmaceutical syringe attachment component to the distal end side along with the pharmaceutical syringe attachment component, so that the injection needle of the needle unit attached to the distal end part of the pharmaceutical syringe unit pierces the skin, or the rear side along with the pharmaceutical syringe attachment component; a second driver that is configured to move a gasket of a pharmaceutical syringe constituting the pharmaceutical syringe unit to the distal end side, so that the pharmaceutical inside the pharmaceutical syringe is injected through the injection needle into the body; a controller connected to the first driver and the second driver being an electrical motor; wherein the pharmaceutical injection device further comprises an attached state detector that detects the attached state of the distal end cap to the main body case, characterized in that the controller during pharmaceutical injection, can execute the normal pharmaceutical injection mode in which the first and second drivers (1008, 1009) are actuated when the attached state detector has detected a state in which the distal end cap has been attached to the main body case, and in which during needle insertion the first driver moves the injection needle to the distal end cap side along with the inner case in a state where the skin is pressed against the distal end side of the distal end cap; and can execute a simple pharmaceutical injection mode in which only the second driver is actuated when the attached state detector has detected a state in which the distal end cap has not been attached to the main body case. a main body case having a pharmaceutical syringe attachment component on its distal end side; the pharmaceutical syringe attachment component having an inner case in which a pharmaceutical syringe unit is attached; a distal end cap that can be removably attached to the distal end side of the main body case; a needle unit having an injection needle, wherein during needle insertion the injection needle protrudes to the distal end side through an opening at the distal end of the distal end cap and pierces the skin; a first driver that is configured to move in a normal pharmaceutical injection mode the pharmaceutical syringe unit attached to the pharmaceutical syringe attachment component to the distal end side along with the pharmaceutical syringe attachment component, so that the injection needle of the needle unit attached to the distal end part of the pharmaceutical syringe unit pierces the skin, or the rear side along with the pharmaceutical syringe attachment component; a second driver that is configured to move a gasket of a pharmaceutical syringe constituting the pharmaceutical syringe unit to the distal end side, so that the pharmaceutical inside the pharmaceutical syringe is injected through the injection needle into the body; a controller connected to the first driver and the second driver being an electrical motor; wherein the pharmaceutical injection device further comprises an attached state detector that detects the attached state of the distal end cap to the main body case, characterized in that the controller during pharmaceutical injection, can execute the normal pharmaceutical injection mode in which the first and second drivers (1008, 1009) are actuated when the attached state detector has detected a state in which the distal end cap has been attached to the main body case, and in which during needle insertion the first driver moves the injection needle to the distal end cap side along with the inner case in a state where the skin is pressed against the distal end side of the distal end cap; and can execute a simple pharmaceutical injection mode in which only the second driver is actuated when the attached state detector has detected a state in which the distal end cap has not been attached to the main body case.