An IP telephony apparatus provides simultaneous SIP communication for multiple IP phones and a method is proposed for the same. The IP telephony apparatus comprises a network connection port connected to a network; a plurality of telephone connection ports connected to a plurality of telephone sets; a voice codec unit connected to the telephone connection ports and used for converting a voice signal to a digital voice packet and for converting a digital voice packet to a voice signal; and an IP telephony allocation unit connected to the network connection port and the plurality of telephone connection ports. The IP telephony allocation unit creates an SIP control block containing an SIP call-leg for a local SIP number, and allocates the SIP control block to a destination telephone set according to the SIP call-leg, whereby the telephone sets have bi-directional digital voice packet transmission with a remote SIP number.