Abstract: A spirit level has a base ruler having a hollow chamber and a leveling bubble unit. The leveling bubble unit includes a bubble tube, a bubble tube base and a fixing base. The fixing base has a limit slot for the bubble tube base. The position on the base ruler where the leveling bubble unit is configured has an inlaying opening. The fixing base of the leveling bubble unit is hidden inside the hollow chamber in a sinking style, such that, when the fixing base is placed into the hollow chamber, the tip end of the fixing base is held inside the inlaying opening. The two sides of the top of the fixing base are respectively configured with elastic clasps, and the tip end of the elastic clasp has a slant resisting surface to resist against the corner of the inner wall of the inlaying opening.