A millimeter wave film circulator with coplanar waveguide structure was designed and fabricated using barium ferrite films with thickness of 10 μm. The film circulator operates without external magnet and shows clear circulation at 34 GHz and 37.6 GHz. Circulation with non-reciprocal effect greater than 15 dB has been observed. The results show that circulator using very thin ferrite films can be realized with coplanar waveguide structure. The film circulator exhibits potential to integrate with MMIC.A millimeter wave film circulator with coplanar waveguide structure was designed and fabricated using barium ferrite films with thickness of 10 μm. The film circulator operates without external magnet and shows clear circulation at 34 GHz and 37.6 GHz. Circulation with non-reciprocal effect greater than 15 dB has been observed. The results show that circulator using very thin ferrite films can be realized with coplanar waveguide structure. The film circulator exhibits potential to be integrated with MMIC.