We first analyze the concrete mechanism of speculative attack on the foreign exchange market which became very prevalent phenomena during the foreign exchange crisis. When the central bank of the domestic country tries to defend the attack by increasing the interest rate, some problems can arise in that the speculative attacks through foreign exchange options market and/or index futures markets can be very successful due to that policy. So the central bank should pay much attention to the microstructure of the financial markets when the defence strategy against speculative attack is determined.