Abstract: A power system stabilization device for the stabilization control of a power system, includes an indicator calculation unit for calculating an acceleration index, which is an index representing the acceleration of a generator for supplying electric power to the power system, by using the generator output, which is the output of the generator, and the generator phase difference that indicates the temporal change of the phase angle of the generator output; a threshold value determining unit for determining whether or not the acceleration index exceeds a preset threshold value; and a control command unit for generating a control command for control details that constitute a correction to the stabilization control, set in advance for the threshold value, when the acceleration index exceeds the threshold value.