To provide a trocar cannula by which a seal member is easily washed and exchanged, maintenance is easily performed at low cost, the seal member hardly comes off and the number of parts is reduced with excellent operability in fixing the seal member.

The trocar cannula 1 is provided with a conduit 6 which is introduced into a body and where a medical implement is put through, an inserting part 2 introducing the medical implement into the body through the conduit 6, a holding part 3 which is arranged at the base end side of the part 2 in order to hold the base end side of the implement which is put through the part 2 and which is provided with an opening 8 which leads to the conduit 6 of the part 2 and seal parts 46 and 48 which are freely attachably/detachably fitted to the opening 8 of the part 3 and are adhered to the implement. The tube 1 is also characterized by providing the seal member 26 for sealing a space between the implement and the part 3 by the seal parts 46 and 48 and a fixing member 25 for fixing the seal member 26 concerning the part 3.