Abstract: A bicycle foot rest is composed of a cramp provided with a shaft body which has a halved ring on the edge. Said halved ring provided with a fixed groove and a halved groove at an appropriate location thereby. A screw fastened therewith between the fixed groove and the halved groove. A revolving body provided a plane with a tapper hole. A frame rod that provided with a receiving hole at the top end thereof uses a screw tube to engage with the revolving body. A guide tube provided cross through inside with the screw tube. A halved head provided with a longitudinal trough hole on the surface. A tension member located in the receiving hole strengthened to the bottom end of guide tube. An elastic member and a steel ball are put orderly into the trough hole of the guide tube. The steel ball is forced to strengthen to the halved ring of the shaft body with a support by the elastic member, and further to strengthen to the fixed groove or to the halved groove.