To obtain a water quality improving material easy to manufacture, excellent in water cleaning function, exerting no adverse effects on a human body and taking no labor in disposal after use, and to provide a water quality improving instrument using the same.

Stalks 10 or branches 10b of kenaf are finely crushed to form kenaf chips 11 which are, in turn, boiled in hot water 13 housed in a boiling container for a predetermined time and the boiled chips are dried to obtain the water quality improving material 15. This water quality improving material 15 is sealed in a water permeable bag 21 to obtain a bagged water quality improving material 20.