A double-blade hair trimming device having a trimmer handle, a blade head, and a driving device disposed inside the trimmer handle. The device has both a thick blade unit used for trimming hard, thick and long hair, and a thin blade unit used for trimming short and fine hair. Hair on the skin can be tidily trimmed by just one shave or one shave in each of two opposite directions. The length of the hair after shaving is less than 0.1 mm.