Disclosed is a 3-dimensional porous mono-polar electrode body that includes a 3-dimensional porous parent substance, which has a 3-dimensional structure including a side and a remaining side that communicate with each other via a plurality of pores arranged in multiple layers and which is made of a metal material to have dimensional stability, and an electrode catalyst layer applied on the 3-dimensional porous parent substance. The 3-dimensional porous mono-polar electrode body is used to remove microorganisms contained in treatment water to thus minimize the consumption of power, which is required to remove the microorganisms, prevent secondary pollution, and ensure the durability of an electrode.