A fluid dynamic bearing is constructed to support stably a rotating body to which a non-uniform force is applied, and a hard disk drive (HDD) employing the fluid dynamic bearing is provided. The fluid dynamic bearing includes a journal bearing part supporting a rotary shaft in a radial direction of the rotary shaft, a thrust part formed at one end of the rotary shaft, a thrust bearing part facing the thrust part and supporting the rotary shaft in a longitudinal direction of the rotary shaft, and a plurality of grooves formed on a surface of the thrust bearing part and/or the thrust part. The plurality of grooves include a first groove group including a plurality of grooves having the same shape and arrangement, and a second groove group adjacent to the first groove group and including at least one groove asymmetric with respect to the grooves of the first groove group.