An organic EL device comprising a lower electrode, an organic light-emission medium and an upper electrode on a support substrate, wherein the water content of the organic light-emission medium is 0.05 wt.% or less and its making method thereof. By constituting the organic EL device like this, it is possible to prevent the shrinkage of light-emission area based on production of the non-emission parts or non-emission spots for a long time at the high temperature condition as well as the room condition.