The present invention relates to an apparatus and method for providing a mobile Internet phone service which can obtain information for a phone call connection in advance and maintain a lightweight session in the case of a first phone call using the power ON of a terminal apparatus or the main phone number for reducing the phone call standby time in an mVoIP call and which can shorten the phone call connection time using the maintained lightweight session for mVoIP calls occurring thereafter and directly entering a P2P call. Accordingly, rapid response and user satisfaction can be improved by significantly reducing the phone call standby time during an attempt to send an mVoIP call, and a P2P call can be connected even during phone call congestion since a separate server system is not connected while the lightweight session is maintained.