An endoscope treatment instrument stopper fitted in a channel opening of a treatment instrument insertion channel of an endoscope, includes a first stopper section having a first treatment instrument insertion hole into which a treatment instrument is inserted; a stopper frame having a stopper section fitting portion, fitted in the channel opening, having therein the first treatment instrument insertion hole of the first stopper section to be opposite the channel opening, and provided with a tearing capable of tearing the stopper frame removed from the channel opening; and a second stopper section having a second treatment instrument insertion hole into which the treatment instrument is inserted, removable from the stopper section fitting portion of the stopper frame, and formed so that the second treatment instrument insertion hole is opposite the first stopper section when the second stopper section is fitted in the stopper section fitting portion.