A communication system for a working machine , wherein the working machine comprises a work vehicle and a working device detachably disposed on a vehicle body of the work vehicle , the communication system comprising: a first communication device configured to be attached to the working device and to transmit, to an outward, a beacon including device information relating to the working device as a broadcasting signal; and a receiving device configured to be provided on the side of the vehicle body and having a receiving part configured to receive the device information transmitted in the broadcasting signal, wherein the first communication device comprises a first outputting part configured to output, as the device information, information including identifying information to the outside, the identifying information identifying the working device , and characterised in that the first communication device further comprises an inertial force detecting part connected to the first outputting part , wherein the first outputting part is configured to be operated by a signal from the inertial force detecting part , and wherein the first outputting part is configured to determine that the working device is operating and to output the beacon, when the inertial force detecting part detects a vibration of the working device continuously for a predetermined time or more. a first communication device configured to be attached to the working device and to transmit, to an outward, a beacon including device information relating to the working device as a broadcasting signal; and a receiving device configured to be provided on the side of the vehicle body and having a receiving part configured to receive the device information transmitted in the broadcasting signal, wherein the first communication device comprises a first outputting part configured to output, as the device information, information including identifying information to the outside, the identifying information identifying the working device , and characterised in that the first communication device further comprises an inertial force detecting part connected to the first outputting part , wherein the first outputting part is configured to be operated by a signal from the inertial force detecting part , and wherein the first outputting part is configured to determine that the working device is operating and to output the beacon, when the inertial force detecting part detects a vibration of the working device continuously for a predetermined time or more. a first outputting part configured to output, as the device information, information including identifying information to the outside, the identifying information identifying the working device , and characterised in that the first communication device further comprises an inertial force detecting part connected to the first outputting part , wherein the first outputting part is configured to be operated by a signal from the inertial force detecting part , and wherein the first outputting part is configured to determine that the working device is operating and to output the beacon, when the inertial force detecting part detects a vibration of the working device continuously for a predetermined time or more. <EOS>