Twenty years have passed since the phenomenon of high-temperature superconductivity was discovered. Studies have diversified from the stage of basic research, and are now focused on the field of application. At the same time, remarkable progress has been made in the field of high-temperature superconducting (HTS) wire made of rare earth (RE) coated materials featuring high critical current values in environments where temperatures are higher and magnetic fields are stronger than ever. In this context, the Railway Technical Research Institute (RTRI) has started a study on the application of HTS wire to magnets for the Maglev system. In this study, it is important to examine the properties of the wire to be used and reflect them in the design of superconducting magnets. Accordingly, the authors have developed an HTS wire-testing device to evaluate the transport current properties of HTS wire in detail under a range of temperature and magnetic field conditions.