with high speed operation a top wire is partly provided with a portion in which a water impermeable belt travels along the inside of its loop dewatering in this portion is effected only on one side that is on the side of the bottom wire also in this portion wrapping angles for the wires and are varied by adjusting the positions of a plurality of rolls and or shoes and to improve the formation and thereafter dewatering on the side where dewatering has been suppressed by the above mentioned belt is also effected application_number US 88297886 A description fig1 shows the preferred embodiment of the present invention in which raw material ejected from a headbox 36 is sandwiched between a bottom wire 33 and a top wire 34 however initially upward dewatering is not effected because a water impermeable belt 35 is traveling along the top wire 34 in addition a breast roll 1 is supported in a vertically adjustable manner reference numeral 2 designates forming boards and numeral 3 designates open rolls which enable adjustment of a wrapping angle of the bottom wire by adjustment of their vertical positions reference numeral 4 designates deflectors which prevent white water removed at the portion of the forming boards 2 from striking against the open rolls so as to not be brought again into inlet nips between the bottom wire 33 and the open rolls 3 the deflector 4 can be adjusted with respect to the engagement thereof with the wire in accordance with the vertical position adjustment of the breast roll 1 or the open rolls 3 the forming boards 2 are also adjustable it is assumed that multiple open rolls 3 and.