An EPDM composition, which comprises a blend rubber comprising 100 parts by weight of blend rubber consisting of 20-80% by weight of EPDM containing 5-ethylidene-2-norbornene [ENB] as one type of diene component and 80-20% by weight of EPDM containing dicyclopentadiene [DCPD] as another type of diene component, and 0.5-10 parts by weight of an organic peroxide. Seal parts obtained by vulcanization molding of the EPDM composition show well balanced characteristics, even if dipped in hot water at high temperatures such as 200° C. for 500 hours or 300° C. for 24 hours, particularly with improved compression set characteristics.