An apparatus comprising two lateral guide devices guiding the paper web at the longitudinal edges of the endless paper web, and a deflection means is provided. With the aid of the deflector the paper web is deflected at least once from its direction of movement to increase the stiffness of the paper web while the paper web is moving between the lateral guide devices. Because of that, the paper web is prevented from ascending the lateral guide devices and a damage to the paper web is avoided when the paper web comes into lateral contact with the lateral guide device.