An endoscopically inserting surgical tool is composed of an elongated flexible cord to be passed through a tool guide channel on an endoscope, and a tool action mechanism mounted on a fore distal end of the flexible cord to be projected out of the tool guide channel. The flexible cord has such a length that, when the tool action mechanism is projected out of a tool exit opening at the end of the tool guide channel, a proximal end portion of the flexible cord still remains outside and rearward of a tool entrance way which is provided on a manipulating head grip of the endoscope as an approach to the tool guide channel. A proximal end portion of the flexible cord is gripped in a rotary tool adjustor which is manipulable to turn the tool action mechanism clockwise or counterclockwise together with the flexible cord in the tool guide channel of the endoscope.