A robot system includes a cooking device to heat a cooking container and having an operation unit configured to select a temperature level; a robot configured to control the temperature level and a cooking time of the cooking device; a dust sensor disposed around the cooking device or on the robot to sense a concentration of foreign substances; a temperature sensor disposed around the cooking device or on the robot to sense a temperature of the cooking container or the cooking device; and a controller configured to control the robot in a safe mode such that at least one of the temperature level and the cooking time is varied according to a danger level determined by a concentration sensing value of the dust sensor and a temperature sensing value of the temperature sensor.