There are provided an apparatus and method for transmitting power headroom information in a multiple component carrier system. This specification discloses a configuration in which a user equipment (UE) receives a Combination Power Headroom Report (CPHR) request message, including a combination indication field indicative of a combination including a plurality of component carriers, from a eNodeB (eNB), calculates a Combination Power Headroom (CPH) calculated in the UE-specific way for the plurality of component carriers, and sends the CPH to the eNB. Accordingly, the complexity of a power headroom report by an UE can be reduced and radio resources used in the power headroom report can be reduced, with the result that uplink transmission performance can be reduced. Furthermore, a scheduler can per form reliable dynamic uplink scheduling in a system to which a carrier aggregation is applied.