To provide an electrode for minute potential measurement in a liquid, easily stored and capable of reducing a period of time until the electrode becomes available during potential measurement.

An electrode comprises: a case 1 having a pair of water flow ports 11 and 12 for communicating the outside and the inside; water flow filters 21 and 22 provided in the water flow ports 11 and 12 of the case 1, respectively; and a plate-like conductor 30 having four holes 31 for water flow and air extraction arranged in the case 1 so as to block a water passage 15 between the filters 21 and 22. The conductor 30 is formed of silver in order to form silver chloride on the surfaces of the conductor after immersed in sea water, and an annular electrode 40 for plating is provided in the almost central part of the outer peripheral surface of the case 1.