1. A method for reporting a power headroom (PH) by a terminal in a wireless communication system, the method comprising:transmitting a first power headroom report (PHR) based on a first uplink resource allocated to a serving cell;
determining whether a second uplink resource is allocated to the serving cell;
identifying whether power backoff due to power management has changed more than a threshold since a transmission of the first PHR, in case that the second uplink resource is allocated to the serving cell; and
transmitting, to a base station, a second PHR based on the second uplink resource, in case that the power backoff due to the power management has changed more than the threshold since the transmission of the first PHR,
wherein the second PHR is transmitted based on a first type PHR of the first type PHR and a second type PHR, and
wherein the first type PHR includes the PH for each of at least one serving cell and bitmap information indicating a serving cell for which the PH is to be reported.