The molecular conformation and crystal structure of an aromatic polyimide, poly[(4,4’diphenylene)pyromellitimide] (PMB), was analyzed by means of X-ray diffraction and a linked-atom least-squares method. X-ray diffraction intensity data were recorded on an imaging plate and measured by the newly developed intensity measuring system. The unit cell was orthorhombic and its dimensions were a = 8.57, b = 5.51, and c (fiber axis) = 16.78 Angstrom. The space group symmetry was Pbam. There were two parallel 1/1 helical chains in a unit cell,one at the corner and the other at the center. The corner and the center one were related by the glide symmetry parallel to the a- and b-axis. Two benzene rings in the biphenyl moiety had a coplanar conformation. The extended polymer chains were aligned along the c-axis in which the pyromellitimide plane and the biphenyl plane were inclined +57 degrees and -58 degrees to the (010) plane, respectively. Because of the glide symmetry, two adjacent pyromellitimide groups were aligned side by side with the same height along the c-axis. The molecular conformations were stabilized only by van der Waals interactions.