Rahman, who passed away last night, is survived by his wife, two sons and a daughter, his family said.
He was 83.
A two-term MLA from Jokihat Assembly seat between 1980-90, he had served as a minister in the Congress governments headed by Chandrashekhar Singh and Jagannath Mishra respectively in Bihar.
His mortal remains were buried with state honours.
Meanwhile, Chief Minister Nitish Kumar mourned the death of Rahman and said that it was an irreparable loss to society and polity in the state.