To provide a rubber composition for a tire bead filler capable of enhancing the heat proof setting and the breaking strength without causing a reduction in hardness, and improving the driving stability as well as the durability.

Such a rubber composition for a tire bead filler is produced by blending 1 to 30 pts.mass of polyrotaxane compound having a cyclic molecule with blocked isocyanate group, a straight chain molecule enclosing the cyclic molecule in a skewer state and closing groups disposed at both ends of the straight chain molecule preventing the cyclic molecule from being detached from the straight chain molecule, 60 pts.mass or more of carbon black whose nitrogen adsorption specific surface area (N₂SA) is 25 to 80 m²/g, 4 to 18 pts.mass of thermosetting resin and a cure agent to the thermosetting resin by 5 to 15 mass%, into 100 pts.mass of rubber constituent comprising 70 pts.mass or more of natural rubber and 30 pts.mass or less of diene rubber having a modified group capable of reacting with isocyanate.