A brewing unit (1) for coffee machine comprising: a brewing chamber (15) that is opened for filing ground coffee, a brewing piston (9) that pressure-tightly closes the brewing chamber (15) and moves reciprocally inside it, and can be adjusted between an open position, a brewing position and a cleaning position when it is at its deepest point within the brewing chamber (15), an inlet port (17) for providing fresh hot water to the brewing chamber (15), an outlet port (13) for brewed coffee, fluidly communicated with the brewing piston (9), a pressure valve (21), that is placed in the brewing piston (9) downstream of the brewing chamber (15) upstream of the outlet port (13), and the brewing piston (9) has a lever (2) that is pivotally mounted therein and which is coupled with the pressure valve (21) in order to be able to open it, and in that a lever free end (23) extends outside of the brewing piston (9) and stands transversally to movement of the brewing piston (9), when the brewing piston (9) reaches the cleaning position the brewing chamber (15) engages and moves the lever (2).