A protrusion of corrugation in a ridge (3) provided at one end (9) of a first fitting body (2) is engaged with one of recesses in a plurality of grooves (6) provided at one end (17) of second fitting body (5) in the lengthwise direction, whereby the degree of overlapping between first fitting body (2) and second fitting body (5) is adjusted. Then, the other end (4) of first fitting body (2) and the other end (7) of second fitting body (5) engaging with the recesses and protrusions of a fluted portion of sensor portion (28) are fixed with a fixing screw (42). Thus, the other end (4) of first fitting body (2) and the other end (7) of second fitting body (5) are drawn near to each other, and a fitting for bicycle (1) is firmly fixed to fork (34).