We developed a newly designed radical beam source for the synthesis of high quality ceramic thin films. Radical species were generated by an electrodeless radio frequency discharge of 13.56 MHz. We succeeded in generation of stable atomic oxygen beam which contained few ionic species. Intensity of the beam was as high as 1.4×10¹⁶ atoms/cm²·s at 5 cm from the end of beam source. Epitaxial thin films of anatase form of TiO₂ and TiN were synthesized on MgO (100) single crystal substrates by using oxygen radical beam and nitrogen radical beam, respectively.