A filling liquid for distribution of an ink jet head of a thermal type, the filling liquid filling a nozzle flow path during distribution of the ink jet head, a hydrophilic region formed on a periphery of an ink discharge port having an opening area of from 100 to 350 μm2, the filling liquid including: an aqueous medium having at least a water-soluble organic compound and water as constituents; and a dye dissolved in the aqueous medium, a concentration of the dye in the filling liquid being 0.2 mass % or more and 1 mass % or less with respect to a total mass of the filling liquid and the concentration of the dye being equal to or less than saturation solubility with respect to the water-soluble organic compound, wherein the filling liquid has a surface tension of 25 mN/m or more and 34 mN/m or less.