Water-purifying agent and water purification method

A water purifying agent, comprising:

• a granulated product of a plant powder, wherein the granulated product of the plant powder is produced by extrusion granulation;
• and
• wherein a Carr's fluidity index of the water purifying agent is 50 or greater, the Carr's fluidity index being obtained by measuring 3 items of the water purifying agent, which are an angle of repose, a degree of compression, and a spatula angle;
• wherein the degree of compression of the water purifying agent is 20% or less;
• and
• wherein the spatula angle of the water purifying agent is 60° or less;
• and
• wherein the granulated product of the plant powder is produced by a producing method that comprises:
• grinding a dried plant to obtain the plant powder having a number average particle diameter of 450 μm or less;
• and kneading the plant powder to which water is added prior to subjecting a resultant to extrusion granulation to obtain the granulated product of the plant powder, and
• wherein an amount of water added to the plant powder during kneading is from 15% by mass to 43% by mass of the plant powder.