There is provided a linkage apparatus for linking a plurality of telephones with one another, including a communication part communicating with the plurality of telephones, a detection part detecting operating states of the plurality of telephones, a determination part determining, on the basis of the detected operating states, whether or not the operating state of a first telephone out of the plurality of telephones has changed to a first state from a third state, and when it is determined that the operating state of the first telephone has changed, determining whether or not the operating state of a second telephone precedently set to be linked with the first telephone is a second state, and a decision part deciding a linkage process that the linkage apparatus makes the second telephone to execute when it is determined that the operating state of the second telephone is the second state.