A device for adjusting a seat height of a personal mobility includes a hollow seat frame extending in a longitudinal direction, a seat support shaft coupled to an upper portion of the seat frame and configured to slide upward and downward, a pedal shaft coupled to a lower portion of the seat frame, a lifting screw shaft extending downward in a state of being fixed to the seat support shaft inside the seat frame, and a rotation screw shaft fastened to the lifting screw shaft inside the seat frame and configured to raise and lower the lifting screw shaft by rotating based on operation of the pedal shaft.