This study was carried out to newly develop the fluxes and filler metals for brazing magnesium alloy AZ31B more easily at lower temperatures. Furthermore, surface preparation was developed to improve the brazeability of magnesium alloy. The main results obtained are as follows. We could successfully develop the fluxes that consisted of chlorides containing Ca ion and Li ion, which made the faying surface of the magnesium alloy active at around 450°C. In addition, we succeeded in developing the filler metals with the melting temperatures lower than 490°C which were Mg-Sn-In system containing a small amount of Al to lower the melting temperature. Surface preparation for magnesium alloy by immersion in aqueous solution containing halogen ion improved remarkably the brazeability of the magnesium alloy. Using the surface preparation together, the fluxes and filler metals could achieve the brazed joints with a high strength equivalent to that of the base metal.