A filter medium is provided. A filter medium according to an embodiment of the present invention comprises: a fiber web layer of a three-dimensional network structure including nanofiber; and a hydrophilic coating layer which covers at least a part of the outer surface of the nanofiber. According to this, a flow rate can be remarkably increased due to the improved hydrophilicity of the filter medium. Also, as the improved hydrophilicity is maintained for a long period of time, the lifespan can be remarkably prolonged. Furthermore, since the modification of a porous structure of the filter medium is minimized during the process of hydrophilization so that the initially designed physical properties of the filter medium can be exhibited in its entirety, the filter medium having chemical resistance, excellent water permeability and durability can be variously applied in the water treatment field.