Abstract: An alarm used for a bicycle having a cover member formed with a number of apertures, the cover member being disposed on a trumpet-like cylinder of the alarm. The alarm comprises a trumpet-like cylindrical body, a mounting piece receptacle bed formed integral with the cylindrical body, a vocal member encased in the cylindrical body, a bellows-like air blower bag, a cover member, and a mounting piece disposed opposite the receptacle bed. The alarm is designed so that air vibrations may be imparted to the vocal member when the air blower bag is biased and when moved back to its initial state.