It is well known that corrosion of steel reinforcement is one of the important factors affecting long-term durability of reinforced concrete (RC) and prestressed concrete (PC) structures. Corrosion usually occurs due to either carbonation or chloride attack. This has been well studied for RC, but not yet for PC. This experimental work is a case study on the long-term performance of prestressed concrete beam. Four prestressed concrete beam specimens including both post-tension type and pre-tension type (pre-cracked or without crack before the exposure) were tested. All beams have been exposed to the real marine environment at Sakata Port, Yamagata prefecture for 20 years, then transferred to the laboratory and stored in a constant temperature and sheltered from the rain for 15 years. Then they were transported to Kyushu University, Ito campus, and tested. Experimental test was addressed for corrosion state of prestressing wires / tendons and load bearing capacity of the beam specimens. This report presents the test results and discussion on durability of PC beam specimens.