To improve the maintainability of a filter as a filter element- replaceable liq. treating filter by making the attachment attaching or detaching and detachment of a lower case to and from an upper case possible to carry out in a short time.

This filter is composed of a bracket part 11a having a liq. inlet path 11d and an outlet path 11e, an upper case 11 consisting of a downward first pipe part 11c having a central passage 11f and a peripheral wall part 11b having a female screw 12a and a lower case 12 provided with a cupped upward second pipe 14 having a male screw 12a on the outer periphery of the open end and supporting the lower end of a filter element 13 at the bottom. The lower case 12 is screwed into the upper case 11 and screwed back to make the element 13 replaceable. In this filter, the male screw 12a on the outer periphery of the lower case 12 and the female screw 11g of the upper case 11 are formed into two rows of several screw threads making 2 pitches P one lead L2 and the lower case 12 is attached or detached to and from the upper case 11 only by half rotation in comparison with the conventional one using one-pitch and one-lead screw.