This paper deals with the occurrence mechanism of the squeal and chatter phenomena generated in a bicycle disk brake and their countermeasures. From the results by bench test apparatus, it was made clear that the squeal is in-plane vibration in the direction of rotor surface with frequency 1kHz caused by the frictional characteristics with negative slope with respect to the relative velocity generated in the vibration system including brake components and spokes, and the chatter is another frictional vibration with frequency 500Hz in which the squeal occurring in the in-plane direction of rotor and the out-of-plane vibration of rotor due to Coulomb friction are superimposed through the internal resonance relation caused by temperature increase of rotor during braking. The measures for squeal and chatter were taken on spokes and hub, and the validity was confirmed by using bench test apparatus.