The 55-year-old Józef Wróbel will become one of four assistant bishops in the Archdiocese of Lublin, where he previously worked as a professor at a Catholic university.
Wróbel formally resigned as bishop on Saturday, and will leave the country on Tuesday. A caretaker will be appointed to run the diocese until the Pope names a new bishop.
Wróbel served as bishop of the Diocese of Helsinki since 2001. He was the fourth Roman Catholic bishop in Finland since independence.
His two predecessors each held the post for more than 30 years. The last was the Dutch-born Paul Verschuren, who served from 1967 until shortly before his death in 2000.
The Roman Catholic Church claims just under 10,000 members in Finland, half of them foreign-born.