This study analyzed whether the Internet, which has established itself as one of the central instruments of economic and business activities, has increased market efficiency by examining whether there are significant differences in average price levels and price dispersion of identical products between the Internet market and traditional offline market. First, comparing the average prices of books and CDs—products with homogeneous characteristics—between online and offline markets revealed that, consistent with predictions, price levels in the online market were relatively lower than in the offline market. This indicates that the development of the Internet contributes to enhancing market efficiency by reducing consumers' information search costs and inducing price decreases in the market. Meanwhile, the price dispersion between online and offline markets was found to be statistically insignificant. However, this result differs from existing research findings that had discovered relatively greater price dispersion in online markets when examining early-stage e-commerce markets, suggesting that the e-commerce market is gradually entering a maturation stage. Furthermore, the trend of narrowing price dispersion in Internet markets is interpreted as evidence that the Internet is ultimately contributing to the enhancement of market efficiency.