A method and device for transmitting a power headroom report (PHR) by a user equipment (UE) in a communication system supporting a plurality of carriers. The method includes transmitting, to an eNode B (eNB), a power headroom report (PHR) related to the plurality of carriers configured for the UE. The power headroom report (PHR) comprises a first type power headroom (PH) and a second type power headroom (PH). While the first type power headroom (PH) is calculated for a power headroom report (PHR) related to a primary carrier and a non-primary carrier, the second type power headroom (PH) is calculated for a power headroom report (PHR) related to only the primary carrier. The second type power headroom (PH) is calculated for case of simultaneous transmission of a physical uplink control channel (PUCCH) and a physical uplink shared channel (PUSCH).