To provide a flame-retardant composition wherein a flame-retardant agent composition made by attaching a flame-retardant agent composition mainly consisting of electrolytes of water-soluble salts (K, Na, Ca, NH4, and alkanolamine), to a film (fiber) component, does not break away owing to external factors (fluid, moisture, ultraviolet, contact, impact, thermal pressure, etc.), the flame-retardant composition which is improved in strength, optical transparency, etc. as well as flame-retardation.

An aqueous solution of a sulfate salt, a carbonate salt, a phosphate salt, a nitrate salt, a sulfamate salt, and an acid sulfate salt (the salts are K, Na, Mg, Ca, NH4, and alkanolamine (C2-3)), is attached to a film sheet composition (central core); and an object including the film (fiber) is joined, with a physical and chemical method, to cover both surface so that the object is processed to the film composition integrated into the three layers.