Plant macrofossil assemblages from the Shobudani Formation in the northern part of Hashimoto City, Wakayama Prefecture, are described. 221 taxa including 21 extinct plants are identified. Six assemblage zones, SB-I to SB-VI in ascending order, are established. The zones SB-II and SB-V are characterized by the occurrence of the members belonging to subarctic and cool-temperate elements indicative of a cool climate. The zones SB-I, SB-III, SB-IV and SB-VI are characterized by the occurrence of the members belonging to warm-temperate and/or subtropical elements associated with some cool-temperate elements, suggesting warm climatic conditions. The coexistence of the members attributed to both subtropical and cool-temperate elements in the zone SB-III suspects warm winters and cool summers. A scarcity of the members belonging to the cool-temperate elements associated with common subtropical and warm-temperate elements in the zone SB-VI indicates warmer summer conditions than in the zone SB-III. Based on the mode of the occurrence of fossil plants, the Shobudani Formation is thought to be early Pleistocene in age. The late early-Pleistocene extinction of Cyclocarya paliurus, Pterocarya aff. stenoptera, and Picea koribai is assumed to a lowering of the winter temperatures. In respect to the extinction of Metasequoia glyptostroboides from the area, a warming of the summer climate and a change in topography together with repeated changes in overall climatic deterioration are suspected.