There are provided a method and an apparatus for scanning in a mobile communication system supporting a multi-carrier. For this, the scanning method includes: in a mobile station supporting a multi-carrier including a primary carrier and a secondary carrier, requesting allocation of a scanning interval to a serving base station by using the primary carrier; receiving a response message for designating the scanning interval and a carrier to be used for scanning from the serving base station; and scanning neighbor base stations by using the carrier designated by the response message in the scanning interval. Transaction data is continuously transmitted and received through the remaining carriers while scanning the neighbor base stations by using the primary carrier or the secondary carrier without interruption.