PURPOSE: To provide a robot sensor teaching method which can teach the sensor actions against a work even if an operator does not set the detecting position of a sensor by an off-line operation.

CONSTITUTION: A sensor action pattern is selected according to the information on the welding area decided by the data given from a work data storing part 503, the data given from a working environment data storing part 501 and a robot data storing part 505, the information on the welding posture decided by the information on the welding area, and the data given from a sensor action pattern storing part 505. Then, the sensor action simulation is carried out to a work like a real device according to the selected sensor action pattern. Thus, the position of the work area to be detected by a sensor is decided and then given to the controller of a robot. Then, the robot knows the position detected by the sensor.