In a unit part of a lead frame for mounting a semiconductor chip, connecting leads and supporting leads extending from a lead frame main body toward a semiconductor chip mounting region are formed. Between each supporting lead and the lead frame main body, a movable part and a spring part for elastically supporting the movable part are disposed. The tip portion of the supporting lead connected with the movable part extends to the inside of the semiconductor chip mounting region in the natural state of the movable part, so that the tip portion butts against the side face of a semiconductor chip when the semiconductor chip is mounted. Thus, the semiconductor chip can be supported and fixed by using a bias force applied by the spring part. The base portions of the supporting leads, the movable part and the spring part do not remain in a package, and hence do not cause a stress in the package and do not increase the volume of the package. Thus, the invention provides a lead frame for forming a LOC package with high reliability which can contain a semiconductor chip having a large area within a regulated volume.