A base station apparatus for use in a mobile communication system includes: a unit configured to generate a reference signal; a unit configured to generate a transmission symbol including the reference signal; a unit configured to transmit the transmission symbol for each sector; and a unit configured to monitor a radio propagation state. The reference signal is generated by multiplying a first sequence formed by a non-orthogonal code sequence which is different at least between an adjacent cell and an own cell, by a second sequence. Whether to form the second sequence by using an orthogonal code sequence which is different among sectors or by using a non-orthogonal code sequence is determined according to the radio propagation state.