To provide a water treatment method and a water treatment apparatus, which ensure a high organic matter removing effect while effectively preventing flux lowering or biofouling caused by organic matter pollution of an RO (reverse osmosis) membrane, when supplying raw water to an RO apparatus and treating it.

In this water treatment apparatus supplying raw water to a reverse osmosis membrane apparatus, the reverse osmosis membrane apparatus supplies raw water at pH of 9.5 or higher, and a reverse osmosis membrane treated with an agent for improving a blocking rate is included. In the water treatment apparatus supplying raw water to the reverse osmosis membrane apparatus, the reverse osmosis membrane apparatus supplies raw water at pH of 9.5 or higher, and has a means for supplying the agent for improving a blocking rate to a primary side. The water treatment method supplying raw water to the reverse osmosis membrane apparatus while the pH is kept 9.5 or higher, has a process of periodically treating the reverse osmosis membrane of the reverse osmosis membrane apparatus with the agent for improving a blocking rate, when the blocking rate of the reverse osmosis membrane apparatus is lowered.