To provide an auxiliary tool for forming a plane of tile surfaces, applicable to various kinds of tiles using the same tool without restriction on the joint width of tiles with a low tool production cost, allowing a non-expert craftsman to perform construction in a short time.

An auxiliary tool for forming a plane of tile surfaces comprises a clip having a bottom plate face, a column part, and a fixing part, and a wedge having a top plate face and an inclined part for fixing. The wedge is inserted between the bottom plate face and the fixing part, so that the top plate face is pressure-contacted with two neighboring tiles. Consequently, the two tile surfaces are aligned along the plane of the top plate face.