To enable positioning an element in the peripheral direction in a vessel, and to eliminate erroneous assemble of a similar element and a fake in the market.

On the inside of a housing 2, four wedge-shaped projecting parts 15 are provided at equally spaced intervals in the peripheral direction of the housing 2, and on the outside of an element 4, fitting grooves 16 each becoming recessed almost like a V-shape are provided. Four of plural vertical grooves 13a provided on a formed filter body 13 are used as the fitting grooves 16 just as they are. When integrating the element 4 into the housing 2, the fitting grooves 16 of the element 4 are fitted on the projecting parts 15 of the housing 2. In this way, the peripheral position of the element 4 to the housing 2 is regulated to enable preventing the deviation in the peripheral position.