Novel measurement method of complex refractive indices of liquid crystal (LC) materials in the ultrahigh frequency region such as microwave and millimeter-wave (MMW) is investigated to reduce the quantity of test sample by using a coplanar waveguide (CPW) substrate, which is known as an excellent planar type waveguide. Although it needs some calibration method for precise measurement, the amplitude and phase properties of the propagating electromagnetic waves are sufficiently sensitive to the extremely small amount of test sample and the basic performance for the loss and refractive index measurements is investigated by using the well known K15 LC material.