To provide a water treatment vessel which can easily store a solid agent for water treatment even if a flow passage is extended.

The water treatment vessel 11 is provided with a cylindrical part 13 having an inflow part 13a into which feed water is made to flow and an outflow part 12a from which treated water is made to flow out. A flow passage is formed at the inside of the cylindrical part 13, and further, the feed water is treated by a solid agent for water treatment stored into the cylindrical part 13. The flow passage is formed by a flow passage wall 16 extending to the upper and lower directions in the cylindrical part 13, and the flow passage wall 16 forms a spiral line shape as seen from above.