A transmission method comprising: a step of generating a first signal series and a second signal series; a step of modulating a first polarized wave using the first signal series and a second polarized wave orthogonal to the first polarized wave using the second signal series; and a step of performing polarization multiplexing of the modulated first polarized wave and the modulated second polarized wave, characterized in that the step of generating includes a switching step that selects at least two steps from a first step configured to generates the second signal series in which a signal identical to an in-phase component of the first signal series is determined as an identical component of the second signal series and a signal identical to a quadrature-phase component of the first signal series is determined as a quadrature-phase component of the second signal series, a second step configured to generates the second signal series in which a signal identical to the orthogonal component of the first signal series is determined as an identical component of the second signal series and a signal caused by performing logical inversion of an identical component of the first signal series is determined as a quadrature-phase component of the second signal series, a third step configured to generates the second signal series in which a signal caused by performing logical inversion of an identical component of the first signal series is determined as an identical component of the second signal series and a signal caused by performing logical inversion of a quadrature-phase component of the first signal series is determined as a quadrature-phase component of the second signal series, and a fourth step configured to generates the second signal series in which a signal caused by performing logical inversion of a quadrature-phase component of the first signal series is determined as an identical component of the second signal series and a signal identical to an identical component of the first signal series is determined as a quadrature-phase component of the second signal series, and the switching step applies said at least two steps to at least part of each time period of the first signal series and the second signal series being divided by a predetermined time length by alternately switching every each time length. a step of generating a first signal series and a second signal series; a step of modulating a first polarized wave using the first signal series and a second polarized wave orthogonal to the first polarized wave using the second signal series; and a step of performing polarization multiplexing of the modulated first polarized wave and the modulated second polarized wave, characterized in that the step of generating includes a switching step that selects at least two steps from a first step configured to generates the second signal series in which a signal identical to an in-phase component of the first signal series is determined as an identical component of the second signal series and a signal identical to a quadrature-phase component of the first signal series is determined as a quadrature-phase component of the second signal series, a second step configured to generates the second signal series in which a signal identical to the orthogonal component of the first signal series is determined as an identical component of the second signal series and a signal caused by performing logical inversion of an identical component of the first signal series is determined as a quadrature-phase component of the second signal series, a third step configured to generates the second signal series in which a signal caused by performing logical inversion of an identical component of the first signal series is determined as an identical component of the second signal series and a signal caused by performing logical inversion of a quadrature-phase component of the first signal series is determined as a quadrature-phase component of the second signal series, and a fourth step configured to generates the second signal series in which a signal caused by performing logical inversion of a quadrature-phase component of the first signal series is determined as an identical component of the second signal series and a signal identical to an identical component of the first signal series is determined as a quadrature-phase component of the second signal series, and the switching step applies said at least two steps to at least part of each time period of the first signal series and the second signal series being divided by a predetermined time length by alternately switching every each time length.