The present invention provides an easily treated filter case shell easily and stably installing a filter case in a container body. The filter case shell comprises a cartridge shaped filter case (6), a container body (1) used in longitudinal insertion, a head (2) with two flow channels for introduction and discharge of treated liquid, a circular member (3) for carrying the container body (1) and the head (2) of the filter shell on periphery surface through rotatable state to use, further, guide mechanism (5) for concentrically positioning the container body (1) and the head (2) between the container body (1) and the circular member (3), such that single-side fastening is prevented, and easy, reliable operation is obtained.