A semiconductor device comprises: a package substrate having a plurality of bonding electrodes arranged in a peripheral region of a main surface thereof and wirings connected to the respective bonding electrodes and electrolessly plated; a semiconductor chip mounted on the package substrate; a plurality of wires connecting pads of the semiconductor chip and the bonding electrodes; a sealing body for sealing the semiconductor chip and the wires with resin; and a plurality of solder balls arranged on the package substrate. The wirings are formed only at the inner side of the plurality of bonding electrodes on the main surface of the package substrate, and no solder resist film is formed at the outer side of the plurality of bonding electrodes. With this arrangement, the region outside the bonding electrodes can be minimized and the semiconductor device can be downsized without changing the size of the chip mounted thereon.