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.