Disclosed is a guide apparatus for use in a folder which is composed of a collect cylinder (F), a cutting cylinder (E), and a jaw cylinder (G). In the guide apparatus, a paper guide (10) is disposed to partially cover the outer circumferential surfaces of the collect cylinder (F) and the jaw cylinder (G) on the downstream side of a narrowest gap between the collect cylinder (F) and the jaw cylinder (G), to thereby define a triangular sheet transfer space (26) in cooperation with the collect cylinder (F) and the jaw cylinder (G). The guide apparatus is composed of a guide plate (1) which is disposed in such a manner as to be able to move between an active position located within the sheet transfer space (210) and a retreat position where the guide plate (1) does not interfere with the sheet transferring from the collect cylinder (F) to the jaw cylinder (G); a position-changeover drive unit (B) for moving the guide plate (1) between the active position and the retreat position; a printing-speed detection unit (C) for detecting the driving speed of a rotary press and outputting a driving speed signal during printing; and a control unit (D) for outputting, upon reception of the driving speed signal from the printing-speed detection unit (C), a position changeover signal to the position-changeover drive unit in order to move the guide plate accordingly.