Fire-extinguishing agent supplying equipment pressurizes a water-based fire-extinguishing agent and supplies the agent via a pipe; and the water-based fire-extinguishing agent is pressurized and supplied via the pipe to an electrification spray head installed in a protection area A, and the jetted particles of the fire-extinguishing agent are electrified and sprayed from the electrification spray head. A pulsed or alternating electrification voltage is applied to the electrification spray head from a voltage application unit 15, and an external electric field generated by applying the voltage between a water-side electrode unit and an induction electrode unit is applied to the fire-extinguishing agent in a jetting process to electrify the jetted particles.