A new process to manufacture semi-solid alloys was proposed. A testing machine was built and a series of experiments were carried out by using Pb-Sn alloys, aluminum alloys and cast irons with aim to characterize the process. In each case, semi-solid alloys with varied levels of fraction solid, from low to high, were successfully manufactured by changing temperature of roll and shoe surfaces, gap between them, roll speed and superheating temperature of supplied molten metal. Through the tests, it has become clear that the proposed process is effective to manufacture various semi-solid alloys. Mechanical properties of the alloys completely solidified after the semi-solid processing were investigated. The flow stress, hardness, elongation and deformability of the semi-solid processed alloys were measured. As the results, it becomes clear that their alloys have better quality than the conventionally cast alloys and, in some cases, their quality is distinctively improved by the semi-solid processing.