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 having relays (111a, 111b) operating in conjunction with each other and connected in parallel, and that is configured to alternatively switch 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; a negative-electrode-side C contact switch that is formed as a twin relay having relays (112a, 112b) operating in conjunction with each other and connected in parallel, and that is configured to alternatively switch 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; and a path switching C contact switch formed as a twin relay having relays configured to operate in conjunction with each other, one of the relays of the path switching C contact switch being configured to switch one of the relays of the positive-electrode-side C contact switch to the connection destination of the first end of the detection capacitor, and another one of the relays of the path switching C contact switch being configured to switch one of the relays of the negative-electrode-side C contact switch to a connection destination of the second end of the detection capacitor. 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 having relays (111a, 111b) operating in conjunction with each other and connected in parallel, and that is configured to alternatively switch 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; a negative-electrode-side C contact switch that is formed as a twin relay having relays (112a, 112b) operating in conjunction with each other and connected in parallel, and that is configured to alternatively switch 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; and a path switching C contact switch formed as a twin relay having relays configured to operate in conjunction with each other, one of the relays of the path switching C contact switch being configured to switch one of the relays of the positive-electrode-side C contact switch to the connection destination of the first end of the detection capacitor, and another one of the relays of the path switching C contact switch being configured to switch one of the relays of the negative-electrode-side C contact switch to a connection destination of the second end of the detection capacitor.