Abstract: A gutter forming machine for forming a gutter having a vertically extended back wall for mounting the gutter on a structure. The gutter forming machine includes a plurality of upper rollers for contacting an upper surface of the material strip and a plurality of lower rollers for contacting a lower surface of the material strip. A lower roller support structure supports the plurality of lower rollers along the path and an upper roller support structure supports the plurality of upper rollers along the path. An auxiliary forming assembly is adapted for contacting a portion of the lower surface of the material strip for forming a portion of the back wall of the gutter. The auxiliary forming assembly comprises a plurality of auxiliary roller assemblies for contacting and guiding a portion of the material strip for forming an extended portion of the back wall of the gutter that extends away from the bottom wall beyond the first plane of the upper lip of the front wall.