To facilitate the work for leading in a cable by partitioning the inside of an explosion-proof container into first and second chambers with a partition wall, connecting the first chamber with the outside of a terminal box through a first cable hole and connecting the second chamber with the inside of a transmitting part body through a second cable hole.

The terminal box 22 comprises a tubular bottomed case 23 of explosion-proof structure having open front, and a cover being applied airtightly to the front opening of the case 23, wherein the inside of the case 23 is partitioned into first and second chambers 26, 27 by a partition wall 25. The partition wall 25 is made of a synthetic resin satisfying explosion-proof requirements and a plurality of terminals 28, 29 are secured to the opposite sides thereof by means of screws 30. A first cable hole 33 communicating with the first chamber 26 and a second cable hole 34 connecting the second chamber 27 with the inside of a transmitting part body 3 are made through the side wall of the case 23 and a part 35 for connecting the case 23 with the connecting part of the transmitting part body 3 is projected integrally.