Ground fault detection apparatus, control method thereof, and control program

A ground fault detection apparatus is configured to perform a detection for a decrease in an insulation resistance in a measurement cycle in which a fluctuation of a second charging voltage as a charging voltage of a first capacitor that is charged in a second charging route in which the first capacitor is connected between a cathode of the battery and the ground is determined to be less than a second threshold value, and a fluctuation of a third charging voltage as the charging voltage of the first capacitor that is charged in a third charging route in which the first capacitor is connected between an anode of the battery and the ground is determined to be less than a third threshold value.