To ensure safety by limiting the rotation of wheels so as not to have speed more than necessary by providing a member moved against the energizing force of a spring by centrifugal force, a moving side braking member provided at this member, and a fixed side brake on the vehicle body side opposed to the moving side braking member.

When the rotating speed of a wheel 12 increases, a weight 17 is moved around along inclined faces 12b, 15a by centrifugal force, and a sliding member 15 is brought into contact with a fixed side braking member 19 provided at a shaft fitting part 13, against the energizing force of an initially caned disc spring 18 so as to apply braking force to the wheel 12. In a vehicle provided with such a braking device 10, the higher the rotating speed of the wheel 12 becomes, the larger centrifugal force of the weight 17 becomes and the more powerful braking force becomes, and the rotating speed of the wheel 12 becomes constant in the end and does not become higher so as to be limited to constant speed. Safety can therefore be ensured.