The invention relates to a rotation information transmission apparatus where wireless communication of data of several Gbps is made possible without miniaturizing the coupler to such an extent that installation is difficult. A first substrate where a first coupler in arc form is provided in an upper portion or a lower portion and a second substrate where a second coupler in arc form of which the length of the arc is shorter than that of the first coupler in arc form is arranged in a location where coupling with the first coupler in arc form is possible are arranged so as to rotate relative to each other by fixing either the first substrate or the second substrate to a non-movable portion and fixing the other of the first substrate or the second substrate to a rotational member.