The cost of production is reduced by effectively utilizing a substrate and reducing testing time. Adjoining two LCD driver chips mounted on a TCP are arranged with their input lead sides and output lead sides arranged opposite to each other, and the input testing terminals and the output testing terminals are commonized. With this arrangement, the mounting pitch of the LCD driver chips is reduced to effectively utilize a substrate, for the achievement of cost reduction. In this case, the input terminals of the same ordinal numbers are arranged so that they receive an electric power or a signal of an identical electric potential as an input when viewed from both ends of the LCD driver chips. Then, both the LCD drivers are concurrently tested by probing at one time by applying an input signal to an input testing terminal common to both the LCD drivers and concurrently measuring outputs from the respective output testing terminals. Cost reduction is achieved by thus reducing the testing time.
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