Provided are a mobile station and a mobile communication method in which, when a secondary cell (SCell) is established in an unlicensed band, received power in the unlicensed band can be efficiently measured and reported to a radio access network. A UE (100) includes an RSSI measurement unit (133) that repeatedly measures RSSI in the frequency band of the secondary cell, a report determination unit (140) that determines, based on an RSSI measurement result, whether to report the measurement result to the radio access network, and a measurement report unit (150) that reports the measurement result to the radio access network. The report determination unit (140) determines that the measurement result is to be reported to the radio access network when the measurement result exceeds a predetermined threshold.