A filler material for an organic electroluminescent element, formed of a resin composition being liquid at 25° C., and containing a hydrocarbon polymer having a number average molecular weight of 300 or more and less than 32,000 and an organometallic compound represented by M-Ln (wherein, M represents a metal atom; L represents an organic group having 9 or more carbon atoms and 1 or more oxygen atoms, and all of L represent the same organic group; and n represents the valence of a metal atom M), wherein a contact angle to silicon nitride is 10 to 40 degrees, and an amount of outgassing other than moisture upon heating at 85° C. for 1 hour is 500 ppm or less in terms of a toluene equivalent, and a method of sealing an organic electroluminescent element using the same.