Holding structure for holding device on fuel tank

1. Field of the Invention A holding structure for holding a device on a fuel tank can be manufactured by small man-hours, and is simple in construction and excellent in vibration isolating performance. The holding structure holds a device () inserted in a fuel tank () on the fuel tank (). The holding structure includes a holding tube () formed integrally with the fuel tank () so as to surround an opening () formed in the fuel tank (), an elastic boot () put on the holding tube () so as to be in close contact with the outer circumference () of the holding tube () and the outer circumference () of a part of the device (), extending outside from the holding tube (), and a fastening device () for fastening the elastic boot () to the respective outer circumferences () of the holding tube () and the device ().