According to an aspect, a network system comprises a ring-type network, and a master transmission apparatus. The master transmission apparatus includes blocking unit, conversion unit and transmission unit. The blocking unit prohibits relay of the transmission frame received through a first virtual transmission line and a second virtual transmission line. The conversion unit changes transmission path information included in the transmission frame from the first virtual transmission line to the second virtual transmission line. The transmission unit transmits the transmission frame including the transmission path information changed by the conversion unit.