Stephen McGowan, who has worked at the company for 14 years, plans to leave in June.
Stephen McGowan, Sun's chief financial officer, plans to step down at the end of June. The company has launched an immediate search for his replacement.
The announcement comes as Sun's board, as well as chief executive Scott McNealy, has come under increasing criticism over the company's operations. Sun's shareholders have taken an activist role.
"It has been a privilege to work at Sun for the past 14 years, and I am proud of the highly capable finance, legal, IT and global business services team we have created," McGowan said in a statement. "I am 100 percent committed to working with Sun's senior management and board of directors to ensure a smooth transition."
Before his promotion to CFO, McGowan previously served as vice president of finance, planning and administration for Sun's global-sales operations.
"While I am very sad to see truly one of the finest CFOs in the industry depart, I am excited for Steve, as he begins a new chapter in his life," McNealy said in a statement.
Sun did not disclose McGowan's post-retirement plans.