An in-vehicle charging apparatus that charges a battery mounted on a vehicle, the in-vehicle charging apparatus comprising: a bridge rectifier that is configured to convert an alternating current supplied from a power supply into a direct current; a ground fault detecting circuit that is provided at a side of the bridge rectifier where the direct current obtained by the conversion of the bridge rectifier flows, that is configured to output a test voltage, and that is configured to detect a ground fault occurring in the in-vehicle charging apparatus, by comparing a test current which changes in response to the occurrence of a ground fault with a predetermined value; and a control section that is configured to control the ground fault detecting circuit, characterized in that the control section is further configured to control the ground fault detecting circuit so that the ground fault detecting circuit outputs respective test voltages of both a first test voltage of a value smaller than a forward voltage of a diode (15a, 15b, 15c, 15d) included in the bridge rectifier and a second test voltage of a value larger than the forward voltage of the diode (15a, 15b, 15c, 15d) included in the bridge rectifier, the control section is further configured to determine that a ground fault occurs in a DC interval on a side of the bridge rectifier where the ground fault detecting circuit is present, if the ground fault detecting circuit detects a test current larger than a first predetermined value when the first test voltage is output, and the control section is further configured to determine that a ground fault occurs in an AC interval on a side of the bridge rectifier which is opposite to the side of the bridge rectifier where the ground fault detecting circuit is present, if the ground fault detecting circuit does not detect the test current larger than a first predetermined value when the first test voltage is output but the ground fault detecting circuit detects a test current larger than a second predetermined value when the second test voltage is output. a bridge rectifier that is configured to convert an alternating current supplied from a power supply into a direct current; a ground fault detecting circuit that is provided at a side of the bridge rectifier where the direct current obtained by the conversion of the bridge rectifier flows, that is configured to output a test voltage, and that is configured to detect a ground fault occurring in the in-vehicle charging apparatus, by comparing a test current which changes in response to the occurrence of a ground fault with a predetermined value; and a control section that is configured to control the ground fault detecting circuit, characterized in that the control section is further configured to control the ground fault detecting circuit so that the ground fault detecting circuit outputs respective test voltages of both a first test voltage of a value smaller than a forward voltage of a diode (15a, 15b, 15c, 15d) included in the bridge rectifier and a second test voltage of a value larger than the forward voltage of the diode (15a, 15b, 15c, 15d) included in the bridge rectifier, the control section is further configured to determine that a ground fault occurs in a DC interval on a side of the bridge rectifier where the ground fault detecting circuit is present, if the ground fault detecting circuit detects a test current larger than a first predetermined value when the first test voltage is output, and the control section is further configured to determine that a ground fault occurs in an AC interval on a side of the bridge rectifier which is opposite to the side of the bridge rectifier where the ground fault detecting circuit is present, if the ground fault detecting circuit does not detect the test current larger than a first predetermined value when the first test voltage is output but the ground fault detecting circuit detects a test current larger than a second predetermined value when the second test voltage is output.