A control method of a washing machine which includes a rotary drum, a balancer mounted to the rotary drum including a ring-shaped channel in which a plurality of balancing modules, each assigned a module identifier, ID, are disposed for attenuating unbalance generated by rotation of the rotary drum, and a position detection sensor (23, 25) configured to detect a position of each of the plurality of balancing modules, the control method characterised by: wirelessly transmitting a movement command that includes a communication ID to the plurality of balancing modules, wherein each of the balancing modules is arranged to move in response to a movement command that has a communication ID which corresponds to the module ID of the balancing module, measuring a first time interval (α, β) between times at which first and second ones of the balancing modules (100a, 100b) are detected by the position detection sensor (23, 25) during rotation of the rotary drum when the positions of the plurality of balancing modules are fixed; measuring a second time interval (α', β') between times at which first and second ones of the balancing modules are detected by the position detection sensor (23, 25) during rotation of the rotary drum when any one of the balancing modules is shifted by a predetermined distance within the channel in response to the received movement command; and confirming correspondence between a module ID of one of the balancing modules and a communication ID of the movement command by comparing the second time interval (α', β') with the first time interval (α, β), wherein: when the comparison of the second time interval with the first time interval indicates an increase or reduction in the time interval in response to a movement direction of any one of the balancing modules, the correspondence between the module ID of any one of the balancing modules and the communication ID of the movement command can be determined. wirelessly transmitting a movement command that includes a communication ID to the plurality of balancing modules, wherein each of the balancing modules is arranged to move in response to a movement command that has a communication ID which corresponds to the module ID of the balancing module, measuring a first time interval (α, β) between times at which first and second ones of the balancing modules (100a, 100b) are detected by the position detection sensor (23, 25) during rotation of the rotary drum when the positions of the plurality of balancing modules are fixed; measuring a second time interval (α', β') between times at which first and second ones of the balancing modules are detected by the position detection sensor (23, 25) during rotation of the rotary drum when any one of the balancing modules is shifted by a predetermined distance within the channel in response to the received movement command; and confirming correspondence between a module ID of one of the balancing modules and a communication ID of the movement command by comparing the second time interval (α', β') with the first time interval (α, β), wherein: when the comparison of the second time interval with the first time interval indicates an increase or reduction in the time interval in response to a movement direction of any one of the balancing modules, the correspondence between the module ID of any one of the balancing modules and the communication ID of the movement command can be determined.