spinning temperatures of respective pitches are consistent usually the viscosities of the spinning pitches largely vary depending upon temperature and therefore the optimum spinning temperature range is narrow therefore in order to spin well it is preferred that viscosities of the pitches at spinning temperatures be substantially approximate for this purpose it is vital that the difference in the softening points of the pitches is not more than 10 u00b0 c the proportion of cross section of the fiber of the pitch based on total cross section in compositing pitches of plural types influences the coiling characteristics of the obtained carbon fibers the larger amount of the pitch having a large coefficient of linear contraction during carbonization has the larger extent of torsion thus good coil shaped fiber bundle can be obtained while the proportion of the pitch having a large coefficient of linear contraction is not limited in the present invention it is preferably within the range of about 5 to about 95 more preferably from 20 to 90 and most preferably from 30 to 80 if the amount of the pitch having a large linear contraction coefficient during carbonization is less than about 5 the extent of coilability will be reduced and its stretchability tends to be reduced if the amount of the pitch having a large linear contraction coefficient during carbonization is more.