To display a message by using a multifunctional telephone set.

An additional box 20i is added to each multifunctional telephone set 10i having a display in addition to a dial key. The additional 20i is provided with plural extended functional keys. Each extended functional key is assigned to each of plural individuals. For example, a message registrar attains an incoming call from a home telephone 40 through a public network L to a PBX 30 housing the multifunctional telephone set 10i. The PBX 30 allows the register to dial a number corresponding to a message by sending a guidance to the register, and stores it corresponding to the extended functional key. When the operator of another arbitrary multifunctional telephone set presses the extended functional key, the PBX 30 analyzes the number corresponding to the stored message, and displays it as a message on the display of the multifunctional telephone set which is being used by the operator.