The object of the present invention is provide a mobile communication system which can improve a communication quality of the mobile communication system as a whole by changing a transmission method for transmitting common information. Each of the mobile stations 200a to 200l comprises a communication quality measurer 230 configured to measure a communication quality of a signal transmitted from the radio station 100a. The radio station 100a comprises a communication quality acquirer 130 configured to acquire the communication quality from the plurality of mobile stations 200a to 200l; a transmission method changer 140 configured to change a transmission method for at least one of an error encoding rate, the number of repeated bits, an interleave length, the number of multiple codes and the number of transmission signal repetitions, in accordance with the acquired communication quality; and a transmitter 110 configured to transmit the signal to the plurality of mobile stations 200a to 200l using the changed transmission method.