To provide a new and improved headbox of a paper/board machine, enabling a conventional tube bank to be omitted.

This headbox of a paper/board machine has a set of valves, each of which is arranged to distribute a flow to a different point in the direction of width of the headbox. Each valve can regulate both the flow quantity of the flow departing from the valve and the consistency of the flow departing from the valve. Further, each valve has an input line for the stock flow and an input line for a diluting flow which is preferably a diluting-water line, and the flows are combined in the valve. The combined flow is passed into the headbox into connection with the stock flow present in the headbox coming from a stock inlet header to be mixed therewith. The headbox has a turbulence generator G arranged after and connected to the stock inlet header in the flow direction. The turbulence generator G has turbulence tubes 10 which open into a slice duct (preferably a slice cone) from which the stock is passed onto a forming wire. The flows are passed from the valves into the tubes 10 in the generator G so that the overall combined flow is distributed into the tubes 10 in the generator G.