To provide a water treatment method capable of substantially omitting conventional pretreatment for removing a suspended substance in raw water in order to enable the simplification of a system, the reduction of an installation area and cost reduction, and a water treatment apparatus therefor.

The water treatment method is constituted so as to perform first stage membrane separation treatment for directly supplying raw water to an internal pressure type hollow fiber separation membrane comprising an internal pressure type hollow fiber reverse osmosis membrane or an internal pressure type hollow fiber nano-filtration membrane to separate the same into permeated water and concentrated water before performing membrane separation treatment for using the permeated water of the previous stage as water to be treated to supply the same to the separation membrane comprising the reverse osmosis membrane or the nano-filtration membrane to separate the same into permeated water and concentrated water on and after a second stage.