A power source device provided with an alternating-current power source and a secondary cell connected to the alternating-current power source, wherein the alternating-current power source is grounded, wherein: - said power source device comprises: - a first switch - configured to selectively connect or cut off said secondary cell and said alternating-current power source, - the first switch being provided between said secondary cell and said alternating-current power source; and - a ground fault sensing means connected to the secondary cell side from the first switch to a ground power line that connects a negative pole side of the first switch and a negative pole of the secondary cell; and - said ground fault sensing means is configured to sense a ground fault in said secondary cell by sensing a reduction in insulation resistance of said secondary cell when said first switch is off, - the ground fault is detected only in a state in which the alternating-current power source is electrically insulated, - an inverter is comprised, - said secondary cell is connected to said alternating-current power source via the inverter configured to convert alternating-current electric power supplied from said alternating-current power source into direct-current electric power and to output the direct-current electric power; and - said first switch is provided between said secondary cell and said inverter, characterized in that- the power source device comprises a DC/DC converter and an electricity leakage sensing means, - the electricity leakage sensing means is electrically connected to each of a pair of power source lines between said first switch and said inverter via said a DC/DC converter, - said electricity leakage sensing means is configured to sense an electricity leakage by comparing an electric current to the ground on a positive pole side and an electric current to the ground on the negative pole side, and - said ground fault sensing means is configured to sense a disconnection in said electricity leakage sensing means when said first switch is on. - said power source device comprises: - a first switch - configured to selectively connect or cut off said secondary cell and said alternating-current power source, - the first switch being provided between said secondary cell and said alternating-current power source; and - a ground fault sensing means connected to the secondary cell side from the first switch to a ground power line that connects a negative pole side of the first switch and a negative pole of the secondary cell; and - a first switch - configured to selectively connect or cut off said secondary cell and said alternating-current power source, - the first switch being provided between said secondary cell and said alternating-current power source; and - configured to selectively connect or cut off said secondary cell and said alternating-current power source, - the first switch being provided between said secondary cell and said alternating-current power source; and - a ground fault sensing means connected to the secondary cell side from the first switch to a ground power line that connects a negative pole side of the first switch and a negative pole of the secondary cell; and - said ground fault sensing means is configured to sense a ground fault in said secondary cell by sensing a reduction in insulation resistance of said secondary cell when said first switch is off, - the ground fault is detected only in a state in which the alternating-current power source is electrically insulated, - an inverter is comprised, - said secondary cell is connected to said alternating-current power source via the inverter configured to convert alternating-current electric power supplied from said alternating-current power source into direct-current electric power and to output the direct-current electric power; and - said first switch is provided between said secondary cell and said inverter, - the electricity leakage sensing means is electrically connected to each of a pair of power source lines between said first switch and said inverter via said a DC/DC converter, - said electricity leakage sensing means is configured to sense an electricity leakage by comparing an electric current to the ground on a positive pole side and an electric current to the ground on the negative pole side, and - said ground fault sensing means is configured to sense a disconnection in said electricity leakage sensing means when said first switch is on.