An object of the present invention is to provide an R-T-B based permanent magnet having a low coercive force and a low magnetizing field, and having a high residual magnetic flux density and a high minor curve flatness even in the low magnetizing field. Provided is an R-T-B based permanent magnet including a main phase crystal grain including a compound having an R2T14B type tetragonal structure and a grain boundary phase existing between the main phase crystal grains, in which R is at least one rare earth element including scandium and yttrium, T is at least one transition metal element including iron, or at least two transition metal elements including iron and cobalt, an average diameter D50 of the main phase crystal grain is 1.00 μm or less, and a content of carbon included in the R-T-B based permanent magnet is 3,000 ppm or more.