A rotation angle detection device may include a magnetic detection member that is configured to detect a rotation angle of a rotation member, a holding member holding the magnetic detection member, and a plurality of wiring members for magnetic detection that are attached to the holding member and are connected to the magnetic detection member. The magnetic detection member has a flat plate-shaped body portion, and a plurality of lead terminals. The holding member holds the body portion of the magnetic detection member in a manner that the body portion can longitudinally slide relative to the holding member. The wiring members for magnetic detection respectively have lead terminal connecting portions. The lead terminals of the magnetic detection member are laid on the lead terminal connecting portions of the wiring members for magnetic detection and bonded thereto.