Abstract: Improved sealing means in rock drilling equipment of the kind comprising casing sections positioned between the drilling unit and the cutter head and housing the drill rod sections. A combined seal consisting of a metal part and a resilient part is positioned between the casing and the cutter head to prevent water and mud from penetrating into the casing. In addition, sealing means are provided to prevent drill water from flowing between the drill rod and the casing in the direction towards the drill chamber, and further means are provided to close off communication between the drill chamber and the annular chamber between the casing and the drill hole wall.