PROBLEM TO BE SOLVED: To provide a Y connector adapter capable of connecting a desired Y connector to a sheath introducer.SOLUTION: A Y connector adapter 100 has a sheath introducer connection part 110 for being connected to a sheath introducer 200 at one end, and has a Y connector connection part 120 for being connected to a Y connector 300 at the another end. The sheath introducer connection part 110 has a protrusion connection pipe 115 that is one end opening of a connection through-hole 130 and through which a valve body 222 of a sheath hub 220 passes to reach the inside of the sheath introducer. The Y connector connection part 120 has a connection port taper part 121 that is the another end opening of the connection through-hole 130 and into which a lure part 331 of a rotator 330 of the Y connector 300 is fitted.
