Precast prestressed concrete (PCaPC) moment-resisting frames have been applied to building constructions over 60 years in Japan. A concern recently arises about the serviceability and the seismic capacity of such existing building structures, which have often been hit by earthquakes or exposed to severe corrosion-prone environment. In this research, the former City Hall of Nandan Town in Awaji Island has been selected as a case study, which was built in 1957 as the first Japanese building using PCaPC beams. Because of its close location to the coast, the target building is considered to be exposed to a severe environment. Moreover, it was severely shaken by the Kobe earthquake in 1995, although noticeable damage was not reported by an inspection carried out several months after the earthquake. Since then several moderate earthquakes have hit it. This paper introduces the building, and describes the results of field inspection, corrosion and strength test results on concrete samples taken from the building. Seismic capacity of the building was evaluated according to the Guideline for Seismic Evaluation and Retrofit for Existing Buildings published by The Japan Building Disaster Prevention Association (JBDPA). The load carrying capacities of the beams are estimated based on the design equations for new constructions specified in the codes and guidelines published by Architectural Institute of Japan or AIJ.