The medical instrument is a medical instrument comprising a connector portion having a tip and a base end, and has a threaded groove for fluid communication between the connector portion and other medical instruments, and the screw groove has a first sidewall provided on the distal end side and a second sidewall provided at the proximal end side of the first side The side wall has a stop portion in which the lead angle has decreased or disappeared.医療器具は、先端と基端とを有するコネクタ部を備える医療器具であって、前記コネクタ部と他の医療器具とを流体連通させるためのねじ溝を備え、前記ねじ溝は、前記先端側に設けられた第１側壁と、前記基端側に設けられた第２側壁と、を有し、前記第１側壁は、リード角が減少又は消失した停止部を有する。
