To provide an antifreeze agent composition for fire extinguishing equipment having high antifreezing performance, which is capable of easily improving fire extinguishing performance as it is incombustible, and easily reducing loads on environment.

The antifreeze agent composition for fire extinguishing equipment contains a water as a main component, and also contains a formate as an antifreezing component. The composition is used as a fire extinguishing agent containing water as a main component for water-based fire extinguishing equipment. For example, it is filled in a pressurized state into a piping forming fire extinguishing sprinkler equipment, and develops an antifreezing effect in winter. A corrosionproof additive is preferably added to the composition for preventing corrosion of piping or the like composed of metallic materials. A concentration of the antifreezing component is preferably 20-60 wt.%.