A sensing unit for a bicycle speedometer is disclosed. The bicycle speedometer has a meter body and the sensing unit for detecting pedaling and generating a signal related to bicycle pedaling. The sensing unit includes a sensor mounted on a bicycle frame and a fixture for carrying a sensed member. The fixture has a fixing end coupled with a bicycle crank and a coupling arm for carrying the sensed member. The fixture allows positional adjustment of the sensed member with respect to the bicycle crank, thereby facilitating aligning the sensed member with the sensor, so as to ensure proper sensing of the sensor to the sensed member.