To prevent rainwater flowing down in an inside passage of a vertical gutter from leaking to an outer wall of a building by fitting fitting pieces arranged on the lower end of the vertical gutter to fitting object pieces arranged on the upper end of the vertical gutter on the inside passage side of the vertical gutter.

Engaging object parts 4 and 4 are arranged on a building side gutter body 1 installed on an outer wall of a building, and engaging parts 3 and 3 are arranged on an outside gutter body 2. The building side gutter body 1 and the outside gutter body 2 are integrally fixed together by engaging the engaging object parts 4 with the engaging parts 3. Fitting pieces 6 and 6 are arranged on the respective lower ends of the building side gutter body 1 and the outside gutter body 2, and fitting object pieces 5 and 5 are arranged on the respective upper ends. A vertical gutter is connected in the lengthwise direction by fitting the fitting pieces 6 to the fitting object pieces 5 on the inside passage 8 side of the vertical gutter. Therefore, a step difference is generated between the lower ends of the fitting pieces 6 and the upper ends of the fitting object pieces 5, and water is prevented from leaking outside the vertical gutter by going over this step difference.