The authors investigated the influence on the properties of vacuum-deposited thin films of organic dyes prepared applying magnetic fields. In spite of a weak magnetic-field intensity (0.1-0.3 T), the effect of the magnetic held could be observed in PL spectra, X-ray diffraction pattern and IR-RAS spectra on p-quaterphenyl (4PO). 4PO molecules are reported to orient almost normal to the substrate, and the molecular orientation of 4PO is disturbed by applying a magnetic field during growth. It is found that some 4PO molecules which are oriented perpendicular to the substrate by a magnetic field will become incorporated into the original alignment domain.