The trocar device (1) has a main portion (2) that includes two ends (3,4). A shaft tube (5) is connected to the end (4) of main portion. A through-opening (6) is adapted for receiving an instrument and extended from the end (3) of main portion to a shaft tube end (7). A sealing unit (8) fixed in main portion is provided with an elastic sealing element with a hollow cylindrical wall. The sealing unit is comprised of a holder clamping-in a portion of the hollow-cylindrical wall of the sealing element such that the sealing element is fixed in the holder.
