A mobile station (1) has a capability to communicate with a base station (2) simultaneously using activated first and second uplink carriers. The mobile station (1) is configured to transmit a power headroom report to the base station (2). The power headroom report includes an information element (ΔPPUSCH) indicating a power difference between first maximum transmission power of the mobile station (1) for the first uplink carrier and second maximum transmission power of the mobile station (1) for the second uplink carrier. It is thus, for example, possible to provide improvement of power headroom reporting (PHR) suitable for uplink carrier aggregation.