A medical instrument for endoscopic surgery, including a sheath tube having a distal and a proximal end and a connecting body arranged at the sheath tube's proximal end area, whereby the sheath tube and connecting body are penetrated in axial direction by a common channel, through which an elongated actuating element passes, an end body connectable to connecting body having a hand grip attached for operating the medical instrument, a locking slider, which is slidably housed in a channel oriented at an angle to the channel within connecting body, whereby the actuation area of locking slider projects from connecting body and can be actuated to locked and free positions using finger pressure, such that the end body coupled to connecting body is positively locked to connecting body in the locked position, and the end body in the free position can be detached from connecting body.