The invention relates to a radio apparatus for estimating a direction from which a received wave arrives and forming a radio transmission channel between a transmitting end of the received wave and itself. The invention aims to maintain stable transmission quality. The radio apparatus of the invention includes: two receiving sections which alternately detect two received waves that have arrived from a same transmitting end to two elements, in every period as an integer multiple of a period of each symbol of the received waves; and an arriving angle calculating section which calculates, in every period, an arriving angle as an inverse function of a difference in two phases which are proportional to a distance between the two elements, given as a function of positions of the elements and the arriving angle of the received waves, and contain a difference in phase shift amounts of the two receiving sections.