An apparatus and method for preventing falsification of a client screen is provided, in which a web server dynamically generates URIs and provides them to clients, thus preventing the falsification of client screens due to a web injection attack or a memory hacking attack. The apparatus includes a random web generation unit for converting an identical web page into random URIs that are randomly generated, at a request of a plurality of clients, generating different random web sources, and providing the different random web sources to the respective clients. A web falsification determination unit compares display web source eigenvalues respectively generated by the clients with respect to any one of the random web sources with a generative web source eigenvalue for the one of the random web sources, thus determining whether screens corresponding to the random web sources displayed on the respective clients have been falsified.