A method for manufacturing a semiconductor device includes preparing a lead frame, mounting a semiconductor element on an obverse face of the lead frame, forming a sealing resin covering the semiconductor element, forming a groove on a reverse face of the lead frame, and removing a portion of the lead frame and a portion of the sealing resin along a disposal region that is narrower than the groove and entirely overlaps with the groove. The preparing of the lead frame includes forming at least one recess located in the disposal region and having an end that is open in the thickness direction. The forming of the groove includes exposing the recess on a side of the reverse face of the lead frame. The removing is performed with reference to the recess.