Abstract: A safety apparatus wherein a sensor (10.sub.n through 15.sub.n, 16) for transmitting object (M) detection information as a reduction in the output signal energy, is used as a human detection sensor, while a sensor (21-26) for transmitting object (M) detection information as an increase in the output signal energy is used as a work piece detection sensor, and drive of a mechanical moving portion is permitted only when the logical OR output of both sensors has a logical value of "1" corresponding to the high energy condition, thereby reliably ensuring excellent operator safety in a fail-safe manner.