A percussion device (1) with a reciprocating percussion piston (3), includes a first chamber (5) that can be pressurized for forward driving of the percussion piston (3) and a second chamber (8) that can be periodically pressurized for back-driving of the percussion piston (3). The percussion device includes at least one driving piston (7) arranged for actuating the back-driving of the percussion piston (3) wherein a portion of said driving piston (7) is arranged to enter into the second chamber (8) for pressure actuating on a driving surface of the driving piston by pressure medium being present in this chamber in the direction of back-driving, wherein the driving piston (7) includes means for back-driving co-operation with the percussion piston (3), and wherein the driving piston (7) is free for axial movement with respect to the percussion piston (3), opposite the direction of back-driving. The invention also concerns a method and a rock drilling machine.