To provide a spin-on filter sufficiently securing a flow path of a fluid to be filtered and having a small pressure loss.

In the spin-on filter 1, an element assembly body 3 includes a compressed coil spring 65 between the bottom face of a case 30 and the lower end face of a filter element 50. When a filter head 2 is clear of the element assembly body 3, the upper end face of the filter element 50 energizes a cover member 34 by the compressed coil spring 65, thus outer peripheral space 71 is so constituted as not to communicate with through-space 36 formed in the cover member 34. Then, when the element assembly body 3 is attached to the filter head 2, the filter element 50 is pushed downward against the case 30 by the filter head 2, and the upper end face of the filter element 50 and the cover member 34 come apart from and together with each other, thus the outer peripheral space 71 is constituted so as to communicate with an inflow hole 8 of the filter head 2 helically inserted into the through-space 36.

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