PURPOSE: To increase the amt. of filtered water per unit time and to prevent clogging of a filtration member for a long time by reducing the resistance for passing watr of a filtration member by regulating the average pore size of the filtration member to 40W90μ.

CONSTITUTION: City water is passed through an inlet 3 of the water and fed at 10l/min to the inside of a case 1 of a main body. The city water is stored in the case 1 and permeates by its head into pores of the filtratin member 9. Each pore of the filtration member 9 has intricated complex shape or branched, accordingly, contaminants are captured by being hitched at manu points of the thickness of the filtration member 9 of the pores while the water pssses through the pores, to achieve thus filtration. The filtrate water flows out of an outlet 4 of the flow. The average pore size of the filtration member 9 is regulated to 40W90μ.