In this paper are presented a new concept concerning on the effective use of conical cavity flow. Because the flow over cavities may cause noise, oscillation, and resonance vibration, most of researches focus on the negative effect of the cavity flow, however, there are also some studies concerning on the effective use of cavities. For example, spike at nose of body is used as an aerodynamic device for drag reduction and/or thermal protection system of the vehicle. In 2003, we proposed an advanced aerodynamic device with conical cavities. This device, which is designated Multi-Row-Disk (MRD), has a cone and some disks, which are placed in the axial direction. Because flows over deep cavities formed between disks are stable, this structure can replace the solid structure without deteriorating aerodynamic performance of streamline objects. We continue the research on the MRD structure for applying to supersonic inlets or airplanes. In the first part of this paper, examination on the conical cavity flow is reported. In the second part, we show wind tunnel results of the supersonic inlet with the MRD structure.