Late Permian (early Kuman) radiolarians are reported and depicted from Sado Island of Niigata Prefecture, central Japan, for the first time. The radiolarian fauna is obtained from mudstone. It is composed of Follicucullus charveti Caridroit et De Wever, FoUicucullus ventricosus Ormiston et Babcock, Entactinosphaera aff. Cimelia Nazarov et Ormiston, Entactinosphaera pseudocimelia Sashida et Tonishi, Hegleria mammilla (Sheng et Wang) and so on. A part of the pre-Tertiary rocks of Sado Island should be correlated to the Permian of the Ultra-Tanba Belt or Joetsu Belt, although they have previously been regarded as one of the Mesozoic accretionary complexes of the Ashio Belt.