A framer in a transmission device that allocates time slots of an optical channel to a logical path, divides client signals received via the logical path to the time slots allocated to the logical path, and transmits the client signals by a plurality of optical suhcarriers using optical wavelengths correlated with the time slots includes: a time slot allocating unit configured to perform a process of reducing a transmission band of the logical path when some of the optical wavelengths are unavailable and changing the time slots allocated to the logical path depending on the reduced transmission band to avoid using the time slots corresponding to the unavailable optical wavelengths.