To automatically open and close a door whose opening/closing direction is unknown in particular, in a method of opening and closing the door by a robot.

The robot includes a robot arm 1 and an end effector 2 of a hand shape for grasping a handle or a shape capable of hooking. The robot moves an end which grasps a door handle in various directions, detects force information by a force detection part 3, and also detects the position displacement of the end calculated by an end position calculation part 4. When a force detected by the force detection part 3 reaches a threshold or higher, the direction is not a correct direction of opening and closing the door, and when the force detected by the force detection part 3 reaches the threshold or lower and the position displacement of the end is observed before and after the trial of an operation calculated by the end position calculation part 4, the direction of opening and closing the door is determined to be correct.