Abstract: The safety device includes an opening/closing cover which isolates a takeout part and an accommodating part of a component feeder unit from each other and which has a sensor for detecting a closed state. The component feeder unit includes the component accommodating part, a feed-out part and the takeout part, and sensors for transmission through voids common to the plurality of set component feeder units. Upon a detection by any one of the sensors during the operation of the machine, the machine is halted. For replacement of the component feeder units, a changeover switch is pressed, by which the detecting function is paused for a specified time period. Thus, a safety device which allows the component feeder units to be replaced even during the operation of the machine can be obtained.