Temperature dependence of the long term deterioration phenomena associated with electrical tree in DGEBA-MDA-SN epoxy resin system under inhomogeneous high electric field wer investigated quantitatively from the viewpoint of fractal analysis. The fractal dimensions were calculated by using scale convering method. The tree structures longer than specific length had fractal properties regardless of applied voltage and ambient temperature. The fractal dimension increased with increasing tree length and saturated at 1.5 to 1.7