Provided are a base station, a mobile station, a method for transmitting calculation parameters for a power headroom and a method for transmitting a power headroom capable of increasing the accuracy of link adaptation by reducing the probability that a power headroom value is out of a reported range. In a base station (100), a PHR bandwidth notifier (105) determines a bandwidth for power headroom calculation to be used for calculating a power headroom by a mobile station (200) for a component carrier to which an unlink allocation signal (UL grant) is not mapped and generates a notification signal containing information on the determined bandwidth for power headroom calculation, and a transmitting means (modulator (106), transmission RF unit (107)) transmits the generated notification signal to the mobile station (200). Specifically, the PHR bandwidth notifier (105) determines a bandwidth for PHR calculation according to an estimated path-loss level.