To provide a portable buttock section washing tool capable of simplifying operation of washing a buttock section, obtaining high washing effect with a small force and capable of being easily carried.

The portable buttock section washing tool includes: an operating portion that is detachably attached to an opening portion of a PET bottle and that pumps liquid in the PET bottle; a movable tube provided in the operating portion; and a liquid discharge portion attached to a tip of the movable tube. A pressure reducing valve may be attached to the operating portion and a feed water pump may be attached to the movable tube.