To compose a composite filter for obtaining water having a high purity usable as water for life and water for medicine from water in which impurities are mixed. Furthermore, to compose an apparatus for obtaining water having a high purity using the filter. Moreover, to configure the apparatus so as to facilitate exchange of the filter. That is, water having a high purity can be obtained by allowing raw water to permeate through a composite filter which consists of a first layer 11 made of fibers, a second layer 12 made of ion exchange resin, a third layer 14 made of activated carbon and a fourth layer 16 made of an unwoven textile. These first layer, second layer, third layer and fourth layer are configured as separate independent filters respectively so that each filter can be exchanged independently. Furthermore, different kinds of filters can be combined dependently on purposes of use.