PURPOSE: To provide a wet forming section of a paper machine which is capable of arbitrarily changing dewatering efficiency in forming rolls and is capable of determining the quality of a textile material web to be simultaneously formed regardless thereof and a method of operation thereof.

CONSTITUTION: The web forming section of the paper machine has a head box 1, two metal wire belts 6 and 7 to wind a forming cylinder 5 over a small section, an position-changeable intake roll 7.1 existing at the beginning end of the small section at the circumference of the forming cylinder and oscillation devices 2, 2.1, 2.2, 2.3 and 2.4 of the head box. The oscillation devices are formed and arranged in such a manner that the release port region of the nozzle of the head box is movable around the circumference of the forming cylinder in order to affect the dewatering efficiently in the forming cylinder and the quality regardless of the dewatering.