Mobile communication systems and radio resource control methods are provided, by which interference between two or more base stations can be suppressed and an inter-cell adjusting control of radio resources for each of the two or more base stations can be simplified in a mobile communication system including two or more base stations, at least a part of each cell of the base stations being mutually overlapped. Two or more cell layers are configured by grouping the two or more base station. An inter-cell adjusting control of radio resources (for example, at least one of a synchronization control of time slots and an allocation control of time slots) between the two or more cell layers is performed. An inter-cell adjusting control of radio resources between two or more base stations included in the cell layer (for example, at least one of a synchronization control of time slots and an allocation control of time slots) for each of the cell layers is also performed.