To improve the performance of the operability for an operator by referring to access level information and executing the masking processing of a function in an HMI terminal based on access level information for the respective operators.

An operator ID input part 101 fetches inputted operator ID and a password and transfers the operator ID and the password to an access level judgment part 102. A mask processing part 105 receives operator ID and an access level, which are transferred from the access level judgment part 102, and holds them. When a request from the HMI terminal 100 itself is received through a request reception/return part 104, a request content is masked in accordance with the access level and it is transferred to common PF/DB 200. The request reception/return part 104 receives the request from the HMI terminal 100 by the operator, receives information on the request content sent from the masking processing part 105 and displays information on the request content to the HMI terminal 100.