noun
study room
A room specifically set aside or used for studying, often in a home or dormitory.
彼はいつも勉強部屋で宿題をしている。
He always does his homework in the study room.
書斎 is a more formal term for a study or library, often implying a private room with bookshelves, while 勉強部屋 is a straightforward, everyday word for any room used for studying.
Compound of 勉強 (study) and 部屋 (room).