System and method for connecting portable information equipment and extension telephone

A system for connecting a portable information equipment and an extension telephone, comprises: an extension telephone connecting device for connecting the portable information equipment to an extension telephone system after authentication through a virtual private network (VPN); and a Voice over Internet Protocol (VoIP) connecting device for connecting the portable information equipment connected to the extension telephone system to the extension telephone connected to the extension telephone system by VoIP. This system enables a temporary staff to make a call from outside to an extension telephone system in a dispatched company while maintaining security.