ULTRAHIGH-PRESSURE SEALING DEVICE AND RECIPROCATIING PUMP

An ultrahigh-pressure sealing device improves sealing performance under ultrahigh pressures and improves durability. The ultrahigh-pressure sealing device (1) is arranged to seal an annular space (C1) between an outer member (2) and an inner member (3) and separates between a high-pressure chamber (RH) and a low-pressure chamber (RL). A bottom ring (4) includes a first inner periphery (4a), a first large-diameter outer periphery (4e), a first small-diameter outer periphery (4f), and a first middle outer periphery (4g). A back-up ring (5) includes a second inner periphery (5a), a second engagement portion (5b), and a second outer periphery (5c). A packing ring (6) includes a third low-pressure-chamber end (6b), a third inner periphery (6a), a third large-diameter outer periphery (6e), a third the small-diameter outer periphery (6f), and a third middle outer periphery (6g). An elastic ring (7) includes a fourth inner periphery (7a), a fourth the engagement portion (7b), and a fourth outer periphery (7c).