For use of the phosphonium salt of general formula (I) as a component of the catalyst for telomerization reaction, it is preferable in view of telomerization reaction data that at least one of R4, R5 and R6 is an aryl group which is not substituted, such as phenyl, tolyl or the like, or an aryl group substituted by di(lower alkyl)amino, --SO3 M or --COOM (where M has the meaning defined hereinbefo