Osaka Stock Exchange introduced J-GATE, a newly trading platform for derivative trading on February 2011．By using the introduction as an exogenous event that increases high-frequency trading in the futures market, this paper investigates whether high-frequency trading in futures
market improve its spot market liquidity. The empirical results provide the evidence that high-frequency trading improve spot market liquidity in terms of spread measures. However, the results find that the
market depth in the spot market is not improved by the high-frequency trading.