A water-capturing or drying agent placed in a hermetically sealed field light emission device for maintaining stable light emission of the light emission device not susceptible to moisture and oxygen for long period of time. The drying agent comprises a compound of polymer formed by bonding M constituting a plurality of organometallic compounds wherein M is a trivalent metal atom with an oxygen molecule. The drying agent is placed in the hermetically sealed container, thereby protecting the field light emission device from being adversely affected by damage from trace amounts of moisture permeating from outside the hermetically sealed container and/or adhered to the inner surface thereof.