The relation between the in-plane orientation of polyimide film and gr
aphitizability was investigated. The degree of in-plane orientation wa
s estimated by means of optical birefringence and ESR technique. The p
olyimide film was found to have non-uniform orientation in the thickne
ss direction because the thinner the film was, the greater the orienta
tion. The inhomogeneity of orientation caused multiphase graphitizatio
n in a film with a composite profile of the X-ray diffraction peak.