Three-dimensional structures of 70 tropical cyclones (TCs) that made landfall in the southern part of the main islands of Japan during 1979-2004 were examined by using the Japanese 25-year Reanalysis (JRA-25) dataset. These 70 TCs had been classified into 5 clusters C1-C5 in a previous study by means of the fuzzy c-means method based on the surface wind fields. A cyclone phase space analysis using three indicators exhibited that the average TC in each cluster has a thermal structure at its particular stage of the structural change in midlatitudes. The average C1 and C5 TCs, both of which were characterized by the area of strong winds concentrated near the cyclone center, were a relatively intense TC at the early stage of the extratropical transition (ET) and a weakening TC with a thermally symmetric structure, respectively. The C2 and C3 TCs, accompanied by the area of strong winds in the right semicircle with respect to the direction of the storm motion, were a mature TC and a thermally asymmetric, weak TC at the late ET stage, respectively. The C4 TC accompanied by strong winds on both right and left sides was a large, mature TC in August or, alternatively, a TC undergoing ET with a strong warm core in the months except for August. Composite analyses indicated that the average TC structure of each cluster is related to the environment characterized by other features such as a trough in the midlatitude westerly, the subtropical high and another TC.