The present disclosure relates to a method of transmitting a Power Headroom Report (PHR) for inter-cell multi transmission/reception point (mTRP) operation in a wireless communication system. In particular, the method includes the steps of: based on a power headroom report (PHR) triggering condition being met, generating a PHR medium access control (MAC) control element (CE) related to a first cell among the plurality of cells; and transmitting the PHR MAC CE including the power headroom information of the first cell to a network, wherein generating the PHR MAC CE comprises setting a power headroom information presence field associated with the first cell to 1, wherein, based on the first cell being associated with at least one second cell, the PHR MAC CE further includes power headroom information of the at least one second cell.