To supply a timing belt which a user can forecast to break in near future as well as a system of forecasting life of the timing belt.
An abnormal sound producing member 16 embedded in the timing belt 10 causes toothed cloth 14 to wear and the abnormal sound to arise by coming into contact with a pulley tooth 28 when it exposes on belt surface due to occurrence of crack or the like. The wear and crack on surface of the timing belt 10 cause failure of lost tooth and cutting, etc. of the timing belt 10 in near future. Consequently, the user can forecast failure of the timing belt 10 induced from some cause by reporting to the user by means of detecting the abnormal sound from the timing belt 10.