A gear assembly may include first and second gear wheels meshing with each other and having a meshing line. The meshing line is formed as a combined line that is positioned between first and second curves to determine a meshing range of the meshing line, so as to extend from a point on the first curve positioned radially inside the second curve in a circumferential direction in which the second curve is radially outwardly spaced from the first curve and to reach a point on the second curve. The combined line is composed of a combination of a plurality of line portions.