Abstract: A surgical instrument has a hollow tubular member, and a pressurization unit that has an outer valve portion, a pressurization device having a movable part configured to generate pressurized fluid when the movable part is moved, and an inner valve portion. The inner valve portion includes a first flow passage that is configured to fluidically connect a first port and a second port of the outer valve portion to each other when the inner valve portion is in a first position, and a second flow passage that is configured between the inner valve portion and the outer valve portion to fluidically connect the first port and a third port when the inner valve portion is in a second position. A sealing system fluidically isolates the second port and the third port from each other at any position of the inner valve portion.