To provide an ideal tool for fall-off prevention for a bolt fastened to a wheel part of a drive shaft during disassembling work of the drive shaft of a rear wheel of an automobile, especially of a large-size automobile.

The fall-off prevention tool 1 for a bolt of a drive shaft is formed, having a circular check plate 2 capable of covering a top part of the drive shaft, a circular ring-shaped magnet 3 fixed to one face of the check plate 2 allowed to be magnetized to the top part of the drive shaft, a protruded part (screw) 5 protruding from the check plate 2 to the central part of the magnet 3, and a handle part 4 protrudingly provided at the central part of the other face of the check plate 2.