PURPOSE: To provide an electrochemical sensor that is disposable after use and is sufficiently inexpensive by providing a body made of an electrolyte composition that can be removed from a bridge means so that it can be replaced by a sample to be tested.

CONSTITUTION: The device has two half cells 80 and 82, the half cells 80 and 82 are exposed to cavities 42 and 44 of a housing 26 and are arranged at an electrode 56 and cavities 42 and 44 that are extended to the outside of the half cells 80 and 82 and closes an electrolyte composition 72 that contacts the electrode 56 and an entrance, and includes film s 74 that contact the electrolyte composition 72 and a bridge that is connected to the entrances of the half cells 80 and 82. Also, it has a body 76 made of the electrolyte composition 72 for covering both the film 74 while being arranged inside the bridge. Then, the body 76 can be removed from the bridge so that it can be replaced by a sample to be tested, thus providing an electrochemical sensor that is disposable and is fully inexpensively.