Cross-sectional transmission electron microscopy observation of CoPtC thin films showed that 10 nm sized ultrafine particles of CoPt typically were elongated along the substrate normal. Analysis of the superposition of 40 micro-electron diffraction patterns showed that there was no preferred crystal orientation of CoPt particles. This superpositioning technique can be applied to thin films, whose X-ray diffraction analysis is difficult due to the small size of the crystals.