PURPOSE: To raise the adsorbing speed of an org substance in water with activated carbon and to eliminate pressure loss generated when water is passed at a high speed, by treating raw water with granular activated carbon while applying treatment due to fibrous activated carbon to treated water to remove an org. substance in water.

CONSTITUTION: Raw water is treated with granular activated carbon at a speed of SV5W50l/h and treatment due to fibrous activated carbon with a monofilament diameter of 5W100μm is applied to the treated water to remove an org. substance in water. By using the fibrous activated carbon with the monofilament diameter of 5W10μm, an adsorbing speed is accelerated 10W200 times as compared with usual granular activated carbon for water treatment and filling density thereof is reduced to 0.05W0.5g/cm2 to enable the prevention of pressure loss. The fibrous activated carbon is formed into a felt or cloth shape and suitably used as the support layer of the granular activated carbon.