To supply large quantities of activated mineral components to animal and plant cells and microorganism cells and improve immunity and propagation power of the cells by using a water purifying agent comprising acids and/or their salts together with bittern.

Bittern obtained by concentrating deep sea water taken out of the deep sea in 200m or more distance from the sea surface or springing and ascending sea water flow can be obtained as a byproduct in sodium salt production from sea water. A mixed solution produced by adding a mineral acid, aluminum chloride, and iron chloride to the bittern is diluted and in the case the resultant diluted solution is added to a water supply tank, an air conditioner, a humidifier, etc., propagation of Legionella pneumophila is suppressed. In this way, immnunity and propagation power of cells of animals and plants and microorganism are improved by supplying mineral components contained in the bittern in activated state and consequently, harvest increase and blight occurrence can be suppressed.