To provide a device for forming a path for inserting an endoscopic surgical instrument in vivo, enabling the position of the endoscopic surgical instrument inserted in a body cavity without removing it from the body cavity.

The device 1 for forming an insertion path in vivo has: a fixing section 4 which can be inserted and fixed into an incised part in the skin; a flexible partition wall 9; flexible tubes 92, 93, 94 and 95 arranged in the flexible partition wall 9; ports 5, 6, 7 and 8 for surgical instrument insertion which are formed at the ends of the flexible tubes 92, 93, 94 and 95; and a port holding mechanism which covers the flexible partition wall 9 and has many port holding sections 11, 12, 13, 14, 15, 16, 17 and 18 for holding the surgical instrument insertion ports 5, 6, 7 and 8; and connection paths 30 for connecting the several port holding sections 11, 12, 13, 14, 15, 16, 17 and 18. The device 1 for forming an insertion path in vivo moves one of the surgical instrument insertion ports held by one of the port holding sections by using the connecting paths 30 to change the port holding section for holding the port.