IC cards (R11, R12, and R21) are issued respectively to users α, β, and γ. An identification code (ID(11)) of a computer (11) supplied to user α and environment information (ENV(11)) that indicates a normal network environment of the computer (11) are recorded in the IC card (R11) issued to user α. When in order to use a computer, a user connects his/her IC card, the identification code and the network environment of the computer to be used are compared with the identification code and environment information recorded in the IC card and different access rights are provided in accordance to the degree of matching. The identification code may be a MAC address of a LAN circuit incorporated in the computer, and the environment information may be a default gateway address or the like. Different access rights can thus be set according to the computer or the network environment that is used.