Disclosed is an apparatus for converting internet protocol addresses, including: an address allocating unit for allocating a first private IP address and a second private IP address of a first IP address format to a first terminal and a second terminal upon an access request of the first terminal; an address generating unit for generating a first public IP address of a second IP address format from a hardware address of the first terminal; an address acquiring unit for acquiring a second public IP address of the second IP address format corresponding to a domain name of the second terminal from a domain name server; a storing unit for storing a mapping table where the first private IP address and the second private IP address correspond respectively to the first public IP address and the second public IP address; and a control unit for providing the first private IP address and the second private IP address to the first terminal.