To provide a device which can perform supervisory control over the safety of field workers from a central supervisory chamber where the field can not be viewed directly.

This device is equipped with a terminal machine 2 which is carried by a field worker and decides and sends information on the position where the field worker moves, a receiver 3 which receives the position information sent from the terminal machine 2, a CPU 1 equipped with a position information deciding function 6 and a position information display function 9 for deciding and displaying the movement position of the field worker, and a CRT 14 which is connected to the CPU 1 and displays the movement position. Further, this device has an operation lock range data setting function 7 of predetermining a movement allowed range wherein the field worker can move and locking the operation of plant equipment when the field worker moves out of the movement allowed range, and an equipment operation lock notifying means 16 which outputs notice of locking the operation of the plant equipment in this case.