A lead frame with a radiator plate on which a semiconductor chip 50 is to be mounted is provided with a radiator plate 30, and a lower surface side lead frame 40 including an upper surface 41 and a lower surface 42. The lower surface side lead frame 40 overlaps and fixes the radiator plate 30 with the lower surface 42 making contact with the radiator plate 30. A through hole 43 piercing the lower surface side lead frame 40 from the upper surface 41 to the lower surface 42 is formed at a position where the lower surface side lead frame 40 overlaps the radiator plate 30, and an opening area of the through hole 43 at the lower surface 42 is larger than an opening area of the through hole 43 at the upper surface 41.