Manufacturing method of semiconductor device and semiconductor device

An improvement is achieved in the reliability of a semiconductor device. After a resin sealing portion is formed to seal a die pad, a semiconductor chip mounted over the die pad, a plurality of leads, and a plurality of wires electrically connecting a plurality of pad electrodes of the semiconductor chip with the leads, the resin sealing portion and the leads are cut with a rotary blade to manufacture the semiconductor device. In the semiconductor device, at least a portion of each of first and second leads is exposed from a lower surface of the sealing portion. End surfaces of the first and second leads as the respective cut surfaces thereof are exposed from each of side surfaces of the sealing portion as the cut surfaces of the resin sealing portion. The distance between a lower side of the end surface of the first lead and an upper surface of the sealing portion is smaller than the distance between an upper side of the end surface of the second lead adjacent thereto and the upper surface of the sealing por