A tablet includes a bismuth-based glass and a refractory filler, wherein the bismuth-based glass comprises, as a glass composition, in terms of mass %, 70 to 90% of Bi2O3, 2 to 12% of B2O3, 0 to 5% of Al2O3, 1 to 15% of ZnO, 0 to 10% of BaO, and 0 to 8% of CuO+Fe2O3; the tablet comprises 1 to 25 vol % of alumina as the refractory filler; and the filling ratio of the tablet is 71% or more.