To provide a method and a device providing a silicon wafer with the same flatness as conventional wafers at excellent productivity even if the wafer is large in diameter.

In this method of grinding semiconductor wafers including simultaneously grinding both surfaces of multiple semiconductor wafers, the wafers are ground by rotating the multiple semiconductor wafers between a pair of upper and lower rotating surface plates in a state where the multiple wafers are held on a carrier so that centers of the multiple wafers are positioned on a circumference of a single circle. The ratio of the area of a circle passing through the centers of the multiple wafers to the area of one of the multiple wafers is greater than or equal to 1.33 but less than 2.0. The rotational speed of the multiple wafers falls within the range of 5 to 80 rpm. The grinding of the multiple wafers with the rotating surface plates are conducted with fixed abrasive grains in the presence of an alkali solution. The double-sided grinder for semiconductor wafers comprises: the pair of upper and lower rotating grinding plates having fixed abrasive grains, a sun gear installed at the rotating center between the rotating grinding plates, an annular internal gear provided on the outer periphery between the rotating grinding plates; a carrier forming planetary gears which are installed between the upper and lower rotating grinding plates and which mesh with the sun gear; and the internal gear; and an alkali solution feeding system.