The present invention is to provide a novel proton conductor comprising a zwitterionic type ionic liquid that can solve a problem of a complicated and enlarged system caused by installing a system of a humidifying device, a recovering device and a resupplying device that are necessary to keep proton transportation stably in an operation environment of a fuel cell. A proton conductor comprising an ionic liquid having a zwitterion wherein an anion and a cation coexist in one molecule, and a proton donor is provided.