The development of a bench-top-type system for simultaneous measurement of X-ray diffraction and Raman spectra has been made to investigate structural changes in the phase transitions of chain molecules such as polyethylene, n-alkane, and so forth from various viewpoints. For the X-ray diffraction measurement an imaging plate or a charge-coupled device camera was used as a two-dimensional detector. For the Raman spectral measurement a miniature Raman spectrometer was used with optical fibers for the irradiation of incident laser beams and collection of scattered signals. For example, in the heating process of the n-C30H62 sample, the phase transition from orthorhombic-to-hexagonal lattices could be detected clearly by the X-ray and Raman measurements. By comparing these two different types of data in detail, an intimate relationship between conformational disordering and rotational motion of molecular chains is detected more clearly than before. Also, similar discussion can be made for the orthorhombic-to-hexagonal phase transition of the geometrically constrained polyethylene sample occurring immediately below the melting point. Another example concerns the structural change in the photoinduced solid-state polymerization of cis,cis-diethylmuconate single crystal. From the shifts in the X-ray reflection position and Raman frequency characteristic of the produced polymer, it was found that the molecular deformation of the polymer chains and lattice strain was induced in the early stage of the polymerization reaction. For the ferroelectric-phase transition of vinylidene fluoride copolymer, the simultaneous measurement was made for collecting triple information of small-angle and wide-angle X-ray scatterings and Raman spectra to know the relationship between the structural change in the crystal lattice and the morphological change in the lamellar stacking mode.