To improve a gutter used for a roof or the like of a house as a general building, and to provide a gutter having a water passage block preventing means for preventing the water passage of a gutter from getting blocked by the flow of the fallen leaves into the gutter and a nest of birds formed in the gutter by providing a top plate part having a rain water passing part such as bored holes or a mesh along the longitudinal direction of an opening part of the upper edge of the gutter main body.

An opening part of an upper edge of a gutter main body having a nearly U-shape cross section or inverted U-shaped cross section is provided with a top plate part having a rain water passing part such as multiple holes or a net along the longitudinal direction of the opening part. The top plate part can be integrally formed with the gutter main body, or the top plate part can be separately formed as a unit, and fixed to the opening part of the upper edge of the gutter main body.