There are provided an electrode tip dressing apparatus and an electrode tip dressing tool for resistance welding, which are miniaturized by reducing a rotational driving-force of a dressing tool. By adjusting a curvature radius of a dressing portion 4 of a dressing tool 2, a contact width, wherein a top electrode tip 5 abuts to the dressing portion 4 of the dressing tool 2, is adjusted from a rotational center of the dressing tool 2 to the outer side of the dressing tool 2. Dressing work done with the dressing tool 2 is thus made to be constant at the whole area of the dressing portion 4, from the rotational center of the dressing tool 2 to the outer side of the dressing tool 2. Accordingly, excess dressing work, which brings decline of productivity, can be avoided, thus enabling to dress the top electrode tip 5 with the minimal dressing work. A rotational driving-power of the dressing tool 2 is thereby reduced, enabling to labor-save and miniaturize the electrode tip dressing apparatus.