GROUND FAULT DETECTION DEVICE

A ground fault detection device comprising a capacitor which serves as a flying capacitor, a switch group which switches between a V0-charging path, a Vcn-charging path, a Vcp-charging path and a charging voltage measurement path for the capacitor, and a controller which controls the switch group and calculates an insulation resistance based on V0, Vcn and Vcp, wherein V0 is a measured value on the V0-charging path, Vcn is a measured value on the Vcn-charging path, and Vcp is a measured value on the Vcp charging path, wherein, if Vcn can be considered as zero, the controller switches to the Vcp-charging path and performs measurement while keeping a charged state of the capacitor, wherein Vcp obtained after discharging the capacitor is subtracted from a measured value obtained from the measurement in order to calculate Vcn.