A power supply apparatus for a sliding door, comprising: a flat cable for electrically connecting devices on a side of vehicle body to the devices on a side of a sliding door mounted on said vehicle body so as to be able to be slid; a vehicle body side fixing portion for fixing said flat cable on said vehicle body; and a door side fixing portion for fixing said flat cable on said sliding door, wherein said flat cable is extracted from said vehicle body side fixing portion and said door side fixing portion in the substantially same direction which is substantially parallel to the sliding directions of said sliding door so that the width direction of said flat cable is maintained to be substantially vertical, wherein a first cable bend restricting portion and a second cable bend restricting portion which are used for turning said flat cable, are respectively provided on the respective extracting sides of said vehicle body side fixing portion and said door side fixing portion and, when said flat cable is turned,an amount of curvature is restricted by said first cable bend restricting portion and said second cable bend restricting portion; wherein said flat cable is extracted from said vehicle body side fixing portion and said door side fixing portion in the closing direction of said sliding door, and wherein, when said sliding door is fully closed, the flat cable is turned by said second cable bend restricting portion and is arranged to substantially linearly run to said vehicle body side fixing portion and, when said sliding door is fully opened, said flat cable is turned by said first cable bend restricting portion and is arranged to substantially linearly run to said door side fixing portion. a flat cable for electrically connecting devices on a side of vehicle body to the devices on a side of a sliding door mounted on said vehicle body so as to be able to be slid; a vehicle body side fixing portion for fixing said flat cable on said vehicle body; and a door side fixing portion for fixing said flat cable on said sliding door, wherein said flat cable is extracted from said vehicle body side fixing portion and said door side fixing portion in the substantially same direction which is substantially parallel to the sliding directions of said sliding door so that the width direction of said flat cable is maintained to be substantially vertical, wherein a first cable bend restricting portion and a second cable bend restricting portion which are used for turning said flat cable, are respectively provided on the respective extracting sides of said vehicle body side fixing portion and said door side fixing portion and, when said flat cable is turned,an amount of curvature is restricted by said first cable bend restricting portion and said second cable bend restricting portion; wherein said flat cable is extracted from said vehicle body side fixing portion and said door side fixing portion in the closing direction of said sliding door, and wherein, when said sliding door is fully closed, the flat cable is turned by said second cable bend restricting portion and is arranged to substantially linearly run to said vehicle body side fixing portion and, when said sliding door is fully opened, said flat cable is turned by said first cable bend restricting portion and is arranged to substantially linearly run to said door side fixing portion.