A communication method including a first tone set moving step of monitoring a transmission line in a steady communication state and moving a tone set if there is no tone ensuring a predetermined S/N ratio, a second tone set moving step of not moving a tone set if there are at least two tones ensuring the S/N ratio and moving a tone set if there is one tone ensuring the S/N ratio and if it is judged that the communication quality can be maintained by moving the tone set in the same tone group, and a tone group moving step of moving a tone group if it is judged that the communication quality cannot be maintained even if the tone set is moved in the same tone group.
