To provide a stable storage container for an anion selective electrode.

The storage container of an anion selective electrode is provided with an ion-sensitive film 4 using an anion exchange resin film and inner liquid. A moisturizer 5 containing any one of water, a hydrophilic macromolecule, an electrolyte, and a hydrophobic compound is provided on a surface in contact with a sample at the opposite side where the ion-sensitive film 4 of the anion selective electrode is in contact with the inner liquid, and the anion selective electrode where space in that a sample with the moisturizer flows is sealed is accommodated along with a member that becomes a steam supply source 8 for sealing. The steam supply source 8 is formed by filling a container formed by a nylon film with solution and covering it with a lid formed by a porous Teflon film, thus maintaining the balance of amount of water at both the sides of the ion-sensitive film for reducing the amount of deterioration in performance.