PROBLEM TO BE SOLVED: To provide an electrodialyzer and an electrodialytic method capable of improving desalination efficiency even when a liquid concentrate of poor flowability is treated.SOLUTION: A electrodialyzer and an electrodialytic method include a cylindrical barrier membrane disposed in a body, a flow path disposed along one of the inner peripheral surface and the outer peripheral surface of the cylindrical barrier membrane to distribute treated liquid, a desalinized liquid housing part disposed along a peripheral surface opposite to a peripheral surface in which the flow path of the cylindrical barrier membrane is disposed, and potential application means for forming a potential gradient so as to subject charge particles in the treated liquid to electrophoresis in the desalinated liquid of the desalinated liquid housing part via the barrier membrane. In a barrier membrane section where the flow path contacts with the desalinated liquid housing part via the cylindrical barrier membrane, the retention time T(hr) of the treated liquid and a maximum clearance distance D(mm) of the treated liquid from the membrane surface of the barrier membrane satisfies a condition of D/T&le；10.【課題】特に、流動性の乏しい原液を処理する場合においても、脱塩効率を向上することができる電気透析装置及び電気透析方法を提供すること。【解決手段】本体内に設けられた筒状の隔膜と、前記筒状の隔膜の内周面又は外周面の何れかに沿って併設され、被処理液を流通する流路と、前記筒状の隔膜の前記流路が併設された周面の反対側の周面に沿って併設された脱離液収容部と、被処理液中の荷電粒子を、前記隔膜を介して前記脱離液収容部の脱離液中へ電気泳動するように電位勾配を形成する電位印加手段と、を備え、前記流路が前記筒状の隔膜を介して前記脱離液収容部に接する膜面区間において、前記被処理液の滞留時間Ｔ（ｈｒ）と、前記被処理液の前記隔膜の膜面からの最大離間距離Ｄ（ｍｍ）とが、Ｄ／Ｔ≦１０の条件を満たす電気透析装置及び電気透析方法。【選択図】図１
