To provide a protective gate which can be installed without pressing a wall.

A rotary shaft 2 provided on one side of a gate door 1 is rotatably pivotted on a bearing 3 which is fixed to the existing door A so that the bearing 3 can be attached and detached. Then the gate door 1 is attached to the existing door A. A drop member 4 is provided to the gate door 1 which can freely advance and withdraw from the gate door 1 to the indoor floor on which the existing door A is provided. Then a suction cup 5 which adheres to the floor with removability is provided at the tip of the drop member 4. The gate door 1 is fixed to the existing door A with removability by a magnetic gripper 6 provided to the existing door A and by a magnet 7 provided to the gate door 1.