Recently, much attention has been given to magnetic refrigeration, because of its energy efficiency and environmental safety. The concept of magnetic refrigeration is based on the magnetocaloric effect (MCE); therefore the development of magnetic materials with a large MCE is strongly desired. In this article we first review the recent development of magnetic refrigerator at temperatures of 20-300K. We then report on the recent progress of magnetic materials with a large MCE. The giant MCE was observed in Er (Co_1-xNi_x)₂, MnAs_1-xSb_x and Mn₃GaC in temperature ranges of below 30K, above 220K and at around 160K, respectively. The origin of the giant MCE in these compounds is the first-order magnetic transition (FOMT). The advantage of utilizing the FOMT system as a magnetic refrigerant material is also described.