The present invention provides a filter for a hemodialysis apparatus, the filter comprises a first cover member, a second cover member and a membrane. The membrane is disposed within the chamber of the first cover member, and the membrane is composed of a first layer of film and two second layer of films, wherein the two second layer of films disposed on the two sides of the first layer of film, respectively. A plurality of first ridges and second ridges are formed on the side of the second cover member, wherein the first and second ridges are spaced from each other and have different widths. Therefore, the present invention can increase the friction force according to the ridges having different widths, and can have high water pressure resistance and the effect of reducing the chances of fluid leakage and erroneous disposition according to the design of non-directional three-layer structures of composite membrance.本發明係提供一種過濾器，用於血液透析迴路裝置，該過濾器包括第一蓋件、第二蓋件及過濾膜。該過濾膜設於第一蓋件之腔室內，且該過濾膜係由一第一層膜及分別結合於該第一層膜兩側上之二第二層膜所構成。該第二蓋件之側面上形成有複數個彼此相間隔且具不同寬度之第一凸紋及第二凸紋。據此，本發明過濾器藉由不同寬度之凸紋，而能具有增加摩擦力之功效，且過濾膜之三層結構及無方向性之複合膜設計，則能具備高耐水壓、減少液體滲漏機率、降低錯置機率之功效。
