PURPOSE: To obtain an additive material for fermentation beds used in fermentation livestock barns or poultry barns by coating granules having elasticity and/or heat insulating properties with a deodorant.

CONSTITUTION: Granules, composed of a synthetic resin such as expanded polystyrene and having a spherical, cylindrical or polygonal outer shape and a hollow or porous inner shape and further elasticity and/or heat insulating properties are coated with a deodorant such as anhydrous iron (bivalent) sulfate to provide an additive material for fermentation beds. The resultant additive material for the fermentation beds is added at 0.2 or more volume ratio to a bed material. The additive material is added to a conventional bed material to sufficiently hold also air permeability without lowering the bed temperature. Thereby, the objective bed material capable of smoothly advancing the fermentation without accumulating feces on the bed and solidifying the bed material is obtained.