A grounding apparatus comprising: a DC power supply; a power conditioner configured to receive DC power of the DC power supply through a DC positive bus and a DC negative bus and to covert the DC power to AC power; an insulated transformer connected to an output side of the power conditioner; a circuit breaker connected to the DC positive bus and the DC negative bus and configured to open a current path between the DC power supply and the power conditioner; and a ground line connecting the DC positive bus or DC negative bus which is provided between the power conditioner and the circuit breaker, to the ground; characterized by a current detector configured to detect a current flowing in the ground line; a fuse inserted in series in a part of the ground line, configured to at least one of: melt when the current flowing in the ground line exceeds a first protection setting value, not destroying the current detector, causing a complete grounding fault, and not to melt when the current flowing in the ground line is less than or equal to the first protection setting value, not destroying the current detector and causing an incomplete grounding fault; and a determination device configured to give an open command to the circuit breaker when the current detected by the current detector exceeds a second protection setting value, which is smaller than the first protection setting value. a DC power supply; a power conditioner configured to receive DC power of the DC power supply through a DC positive bus and a DC negative bus and to covert the DC power to AC power; an insulated transformer connected to an output side of the power conditioner; a circuit breaker connected to the DC positive bus and the DC negative bus and configured to open a current path between the DC power supply and the power conditioner; and a ground line connecting the DC positive bus or DC negative bus which is provided between the power conditioner and the circuit breaker, to the ground; characterized by a current detector configured to detect a current flowing in the ground line; a fuse inserted in series in a part of the ground line, configured to at least one of: melt when the current flowing in the ground line exceeds a first protection setting value, not destroying the current detector, causing a complete grounding fault, and not to melt when the current flowing in the ground line is less than or equal to the first protection setting value, not destroying the current detector and causing an incomplete grounding fault; and a determination device configured to give an open command to the circuit breaker when the current detected by the current detector exceeds a second protection setting value, which is smaller than the first protection setting value. melt when the current flowing in the ground line exceeds a first protection setting value, not destroying the current detector, causing a complete grounding fault, and not to melt when the current flowing in the ground line is less than or equal to the first protection setting value, not destroying the current detector and causing an incomplete grounding fault; and a determination device configured to give an open command to the circuit breaker when the current detected by the current detector exceeds a second protection setting value, which is smaller than the first protection setting value.