biographer
A person who writes biographies; a straightforward compound of 伝記 (biography) and 作者 (author).
He is the biographer of a famous politician.
伝記 means 'biography' (the work itself), while 伝記作者 refers specifically to the person who writes it.
作者 is a general term for 'author' or 'creator'; 伝記作者 narrows it to a biographer.
Compound of 伝記 (biography) and 作者 (author).