To reduce data volume being managed at a branch control station and make it possible to change the state of control at a control point highly precisely.

A central computer 110 has control points 221A to 223B at a substation, a central data memory 111 which stores symbolized data of the state of control, a change indicator 112 which indicates changes of the control state, and a central transmitter 113 which transmits the changed data to computers 210A and 210B at branch stations. These computers 210A and 210B have control points 221A to 223B, data memories 211A and 211B which store symbolized data of the state of control at the branch stations, data comparators 212A and 212B which compare changed data from the central control office and data stored in the memories 211A and 211B and which identify mismatch of the data stored in the memories 211A and 211B and change data 310A and 310B, and control change sections 213A and 213B which change the control points having a mismatch to the state of control in the change data 310A and 310B.