A new type of position sensing device (PSD) is proposed in this paper. The proposed PSDs are composed of two-dimensional grating dots. The grating dots of a new PSD can diffract an incident laser beam into many spots. By identifying the maximum and minimum values of the designed numbers of the diffracted spots, the one- or two-dimensional position of the center of the laser beam can be precisely determined. Because the operations are very easy and the mass-production costs are cheap for the proposed PSDs, the PSDs are useful.