The temperature dependence of the X-ray fiber diagram and polarized infrared spectra has been measured successfully for the first time for the delta form of uniaxially oriented syndiotactic polystyrene, which was obtained by dipping the uniaxially oriented samples into organic solvents, for example toluene. The delta form is known to transform to the gamma form in a broad temperature range by purging out the solvent molecules. It has been confirmed that no other form like empty delta form appears during this delta to gamma transition. At higher temperatures around 190-200 degrees C the gamma form was found to transform to the mixture of alpha and beta forms, not simply to the alpha form as having been reported so far. The DSC thermogram showed an endothermic peak followed by an exothermic peak in the course of transition from the gamma form to alpha (and beta) form. These thermal peaks had been speculated to reflect the melting of the gamma form followed by the recrystallization into alpha (and beta) form. But, judging from the clear X-ray diffraction diagram of highly oriented alpha (and beta) form, the molecular chains must keep the orientation almost perfectly during this transition. The infrared spectra also show the well-oriented chain conformations of T(2)G(2) and all-trans types during the transition. The gamma form has been speculated to transform transiently to a disordered state without losing the chain orientation and then transform into more regular alpha (and beta) form.