To provide a retaining member capable of preventing the rattling and the failure in locking to a mounted member.

A retaining tool 30 is formed by connecting bases 32, 33 and pressing plates 52, 53 capable of holding mounting seats 22, 23 of a fuel tank 20 between the bases 32, 33, through hinges 57. A shaft part 65 is vertically mounted on the bases 32, 33, and elastic locking pieces 62 to the shaft part 65 are formed on the pressing plates 52, 53. Further a plurality of locking teeth 66 are formed on the shaft part 65 along the axial direction of the shaft part 65 in a plurality of stages, and the elastic locking pieces 62 are selectively locked to the locking teeth to adjust the locking positions of the pressing plates 52, 53 to the shaft part 65 in the axial direction of the shaft part 65. Accordingly, the retaining tool 30, furthermore fuel pipes 10, 11 can be surely mounted on the fuel tank 20 without rattling even when the dispersion in the total thickness of a joint flange 21 including a skin 27 is found.