We have been investigating basic characteristics of an Imaging Plate to apply it for ultraheavy cosmic ray dE/dx detector. To determine the kind of nuclide in accuracy, excellent angular resolution and excellent energy resolution are required. So we have measured them using heavy ion accelerator. As the results, we recognized that the angular resolution can be less than 0.4° if two Imaging Plates are distant more than 1 cm. By the way, the energy resolution is at most 30% at present and the energy resolution does not depend on the deposited energy. It indicates that the photon statistics is not dominant for the energy resolution but that the other unknown factor should be dominant. From beam experiments, we recognized that the energy resolution is not affected by neither fading effect nor background accumulation.