An image forming apparatus. The image forming apparatus performs security management functions such as security transmission and security printing of data stored in a hard disk of the image forming apparatus and shared with a plurality of host computers through a network, to which a security tag is added for the security of the data so as to increase the security of the data. The image forming apparatus is connected to the network to be shared with the host computers to receive and store data transmitted from the host computers, and includes a storage device to store IP address information of a host computer which transmitted data and security data to which a security tag is added for the security of the transmitted data corresponding to the IP address information, and an image forming controller to perform security management function of the security data.