The present invention provides an R-T-B based sintered magnet that inhibits the demagnetization rate at high temperature even when less or no heavy rare earth elements such as Dy, Tb and the like are used. The R-T-B based sintered magnet comprises R2T14B crystal grains and two-grain boundary parts between the R2T14B crystal grains. Two-grain boundary parts formed by a phase containing R, Cu, Co, Ga and Fe with a ratio of 40≦R≦70, 1≦Co≦10, 5≦Cu≦50, 1≦Ga≦15, and 1≦Fe≦40 (wherein, R+Cu+Co+Ga+Fe=100, and R is at least one selected from rare earth elements) exists in the magnet.