PURPOSE: To use a single caliper bracket to cope with changing of an external diameter of a disk rotor by providing an adjusting means, which variably adjusts a relative distance between an axle and a brake caliper, in an axle inserting part of the caliper bracket.

CONSTITUTION: An adjust means 36 for variably adjusting a relative distance B between an axle 9 and a brake caliper 15 is provided in an axle inserting part 33 of a caliper bracket 16. This adjust means 36 is formed of a long circular hole 37 drilled in the axle inserting part 33 and a spacer 38 closely fitted to this long circular hole 37. In the long circular hole 37, its major axis has a linear part over a length C, and in the spacer 38, a bore 39 of closely inserting the axle 9 is provided to be offset to one side. Since the caliper bracket 16 is engaged with the axle 9 through this spacer 38, by reversing its front and rear, the caliper bracket 16 can be displaced forward by the length C relating to the axle 9.