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