A ground fault detection apparatus that is connected to a non-grounded high-voltage battery and detects a ground fault of a system provided with the high-voltage battery, the ground fault detection apparatus comprising: a control unit; a detection capacitor that operates as a flying capacitor; a positive-electrode-side first resistor (Ra) connected to a positive-electrode side of the high-voltage battery; a negative-electrode-side first resistor (Rb) connected to a negative-electrode side of the high-voltage battery; a positive-electrode-side second resistor having a first end grounded and a second end, a voltage of the second end being measured by the control unit; a negative-electrode-side second resistor having a first end grounded; a positive-electrode-side C contact switch that is formed as a twin relay in which a first relay and a second relay operate in conjunction with each other and alternatively switches a connection destination of a first end of the detection capacitor between a path including the positive-electrode-side first resistor and a path including the positive-electrode-side second resistor based on an instruction from the control unit; and a negative-electrode-side C contact switch that is formed as a twin relay in which a third relay and a fourth relay operate in conjunction with each other and alternatively switches a connection destination of a second end of the detection capacitor between a path including the negative-electrode-side first resistor and a path including the negative-electrode-side second resistor based on an instruction from the control unit, wherein the first relay is disposed so as to alternatively switch the connection destination of the first end of the detection capacitor between the path including the positive-electrode-side first resistor and one of contacts of the second relay, the second relay functions as a change-over switch that switches a connecting state of a connected contact of the first relay and the positive-electrode-side second resistor to an off state while the first relay is being switched to the path including the positive-electrode-side first resistor, the third relay is disposed so as to alternatively switch the connection destination of the second end of the detection capacitor between the path including the negative-electrode-side first resistor and one of contacts of the fourth relay, and the fourth relay functions as a change-over switch that switches a connecting state of a connected contact of the third relay and the negative-electrode-side second resistor to an off state while the third relay is being switched to the path including the negative-electrode-side first resistor. a control unit; a detection capacitor that operates as a flying capacitor; a positive-electrode-side first resistor (Ra) connected to a positive-electrode side of the high-voltage battery; a negative-electrode-side first resistor (Rb) connected to a negative-electrode side of the high-voltage battery; a positive-electrode-side second resistor having a first end grounded and a second end, a voltage of the second end being measured by the control unit; a negative-electrode-side second resistor having a first end grounded; a positive-electrode-side C contact switch that is formed as a twin relay in which a first relay and a second relay operate in conjunction with each other and alternatively switches a connection destination of a first end of the detection capacitor between a path including the positive-electrode-side first resistor and a path including the positive-electrode-side second resistor based on an instruction from the control unit; and a negative-electrode-side C contact switch that is formed as a twin relay in which a third relay and a fourth relay operate in conjunction with each other and alternatively switches a connection destination of a second end of the detection capacitor between a path including the negative-electrode-side first resistor and a path including the negative-electrode-side second resistor based on an instruction from the control unit, wherein the first relay is disposed so as to alternatively switch the connection destination of the first end of the detection capacitor between the path including the positive-electrode-side first resistor and one of contacts of the second relay, the second relay functions as a change-over switch that switches a connecting state of a connected contact of the first relay and the positive-electrode-side second resistor to an off state while the first relay is being switched to the path including the positive-electrode-side first resistor, the third relay is disposed so as to alternatively switch the connection destination of the second end of the detection capacitor between the path including the negative-electrode-side first resistor and one of contacts of the fourth relay, and the fourth relay functions as a change-over switch that switches a connecting state of a connected contact of the third relay and the negative-electrode-side second resistor to an off state while the third relay is being switched to the path including the negative-electrode-side first resistor.