An evaluation method for insulation performance of an insulator, the evaluation method comprising: a step α of applying a DC voltage to a first insulator on a prescribed applying condition, and measuring an integration value of a current flowing through the first insulator from a start of application of the DC voltage until an elapse of a prescribed time period after an end of application of the DC voltage; a step β of applying a DC voltage to a second insulator on an applying condition that is identical to the applying condition in the step α, and measuring an integration value of a current flowing through the second insulator from a start of application of the DC voltage until an elapse of a prescribed time period after an end of application of the DC voltage; and a step γ of comparing (i) a first graph showing a relation between an elapsed time period and the integration value that are obtained in the step α and (ii) a second graph showing a relation between an elapsed time period and the integration value that are obtained in the step β, to evaluate a difference between insulation performance of the first insulator and insulation performance of the second insulator due to application of the DC voltage, each of integration values being obtained by a current integrator including a capacitor connected in series to a corresponding one of the first insulator and the second insulator, and a voltmeter configured to measure a voltage applied to the capacitor, the current integrator being configured to measure each of the integration values based on a measurement result of the voltmeter, the applying condition including a voltage raising operation for raising a voltage from 0 kV to a prescribed final attained voltage, a voltage holding operation for holding the final attained voltage for a fixed time period, a discharge operation for discharging the capacitor while stopping application of a voltage, and a grounding operation for grounding the capacitor. a step α of applying a DC voltage to a first insulator on a prescribed applying condition, and measuring an integration value of a current flowing through the first insulator from a start of application of the DC voltage until an elapse of a prescribed time period after an end of application of the DC voltage; a step β of applying a DC voltage to a second insulator on an applying condition that is identical to the applying condition in the step α, and measuring an integration value of a current flowing through the second insulator from a start of application of the DC voltage until an elapse of a prescribed time period after an end of application of the DC voltage; and a step γ of comparing (i) a first graph showing a relation between an elapsed time period and the integration value that are obtained in the step α and (ii) a second graph showing a relation between an elapsed time period and the integration value that are obtained in the step β, to evaluate a difference between insulation performance of the first insulator and insulation performance of the second insulator due to application of the DC voltage, each of integration values being obtained by a current integrator including a capacitor connected in series to a corresponding one of the first insulator and the second insulator, and a voltmeter configured to measure a voltage applied to the capacitor, a capacitor connected in series to a corresponding one of the first insulator and the second insulator, and a voltmeter configured to measure a voltage applied to the capacitor, the current integrator being configured to measure each of the integration values based on a measurement result of the voltmeter, the applying condition including a voltage raising operation for raising a voltage from 0 kV to a prescribed final attained voltage, a voltage holding operation for holding the final attained voltage for a fixed time period, a discharge operation for discharging the capacitor while stopping application of a voltage, and a grounding operation for grounding the capacitor. a voltage raising operation for raising a voltage from 0 kV to a prescribed final attained voltage, a voltage holding operation for holding the final attained voltage for a fixed time period, a discharge operation for discharging the capacitor while stopping application of a voltage, and a grounding operation for grounding the capacitor.