A method for transmitting a midamble in a radio communication system is provided. The method includes: allocating a radio resource of a carrier for the midamble, and transmitting the midamble by using the allocated radio resource, wherein the carrier includes a used band allocated for transmitting a signal and a guard band allocated for preventing interference from occurring in the used band, and the midamble is allocated to a radio resource including the guard band. Accordingly, a midamble which can be used in both a user equipment operating at a narrow band and a user equipment operating at a wide band can be transmitted when a radio communication system is in a multi-carrier mode. Further, the midamble can be transmitted also in a guard band, thereby improving accuracy of channel estimation.