In a power system voltage reactive power monitoring control device, a balance between the power system voltage and the reactive power can be maintained even when, for example, the output of renewable energy varies over time due to the weather, or the power supply configuration or system configuration changes, and the economic efficiency can be improved. In the power system voltage reactive power monitoring control device, which supplies transmission data to individual devices capable of adjusting the voltage and the reactive power of a power system, indices indicating the stability of the power system are used to determine one or more target value restrictions, information about the target value is obtained from the target value restrictions, transmission data containing information about the target value is supplied to the individual devices, and the voltage and reactive power at the relevant installation site are adjusted by the individual devices.