A method and apparatus for transmitting a cause value related to a small cell in a wireless communication system is provided. An evolved NodeB (eNB) of a small cell receives a request message form a macro cell, and as a response to the request message, transmits to the macro cell a failure message including a cause value related to the small cell. The cause value related to the small cell can indicate the reason why the small cell which is in an “off” state cannot shift to an “on” state, and the failure message can be any one of a handover preparation failure message, a cell activation failure message, or a secondary evolved NodeB (SeNB) addition failure message.