PROBLEM TO BE SOLVED: To provide a ciliates expellant having a plant-derived component having a small effect on human and other living organisms as an effective ingredient, and exhibiting great effects in extermination of ciliates； expelling method of ciliates； and a water cleaning agent.SOLUTION: A ciliates expellant contains sulforaphane as an effective ingredient, where the sulforaphane is given as one, two or more forms selected from the following group (A): a chemically synthesized product, sulforaphane isolated from a plant and purified, an extract from plants containing sulforaphane, a plant containing sulforaphane, crushed matter and/or pulverized matter of a plant containing sulforaphane, an extract of plants containing a glycoside of sulforaphane, a plant containing a glycoside of sulforaphane, crushed matter and/or pulverized matter of a plant containing a glycoside of sulforaphane.
