An information processing system capable of appropriate precise access control is provided. The information processing system of this invention includes an access controller capable of data transmission/reception, and a computer system connectable to a network via the access controller. The computer system includes an acquiring unit for acquiring user identification information for identifying a user, and application identification information for identifying an application which accesses the network, and an adding unit for generating an IP address on the basis of the acquired user identification information and application identification information, and adding the IP address to data to be transmitted via the application. The access controller includes an access control unit for controlling access to the network on the basis of the IP address added to the transmitted data.