Abstract: A surgical instrument is disclosed which is suitably adapted for use in operations to be performed under an endoscopic surgery. This surgical instrument comprises an elongate main body of the instrument, a leading end part disposed on the leading end side of the main body of the instrument and endowed with surgically operating member for producing an open-close motion or a rotary motion, a manipulating part for effecting remote control of the surgically operating member, and an elongate transmitting member for transmitting the operation in the manipulating part to the leading end part mentioned above. It is provided in or near the leading end part with a locking mechanism for regulating the motion of the transmitting member relative to the leading end part and fixing the posture of the surgically operating member.