PURPOSE: To eliminate useless projection by storing a helical antenna into a handset when the handset is placed onto a key telephone set main body.

CONSTITUTION: When a helical antenna 1 is contained into a handset, the antenna 1 is pushed in to release a stopper 4, the antenna 1 is sunk into the main body and a stopper 3 is active by pressing the antenna further and then the antenna is fixed in the inside of the handset. On the other hand, when a switch 2 is depressed to release the stopper 3, a spring is energized, the antenna appears at the outside, the stopper 3 is activated and the antenna is fixed at the outside of the handset. Thus, the helical antenna 1 is contained in the inside of the handset. Then the size of the handset is made compact and the contact with other material is reduced.