The filter medium is a filter medium which uses a liquid containing oil and water as a separation target, and has a channel for the liquid. The filter medium includes a base constituting the channel, and one or more of nitrogen-containing fluorine compounds which are provided on at least a portion of a surface of the channel. The nitrogen-containing fluorine compound includes an oil-repellency imparting group and any one hydrophilicity imparting group selected from a group consisting of an anion type, a cation type, and an amphoteric type, in a molecule.