A stencil mask for back electrodes of a solar cell comprises a plurality of back electrode openings, each back electrode opening comprising a main opening, and multiple sub-openings allowing conductive paste to slowly spread. The sub-openings are formed along both sides of the main opening at a distance therefrom and are arranged adjacently to each other. The area around the outer edges of the back electrodes gradually slope downward due to the sub-openings, and thus the overlapping portion with a back surface field does not protrude upward and has a similar height to the central part of the back electrodes. Due to the above, the frequency of occurrence of defect during ribbon adhesion can be lowered and adhesiveness of the ribbon can be enhanced, and durability of the mask for printing back electrodes can be improved to thus reduce expenses.