An antenna cable break detector used with a construction machine wireless communication apparatus to detect a break in an antenna cable. The antenna cable 4 includes a central wire 6 and an armor wire 7 that is positioned concentrically outside the central wire. One end of the central wire and the armor wire is connected to a communication device. The other end of the central wire is connected to an antenna 3. The other end of the armor wire is grounded. The antenna cable break detector has a direct current shutoff device that is connected to the armor wire to shut off the flow of direct current 15 from the armor wire to the communication device. There is also a current shutoff detection device that is connected to the armor wire to detect the shutoff of the flow of a direct current to the armor wire.