Viscoelastic properties of poly(isoprene-b-styrene) in dioctylphthalate under steady shear flow were measured near the order-disorder transition temperature. In ordered states, first normal stress difference N-1 is proportional to shear rate gamma at low gamma region, but becomes proportional to gamma(2) at the high gamma region, similar to the N-1 behaviour of polymer blends undergoing shear-induced homogenization. Because the existence of microdomains was confirmed at the high gamma region by the flow birefringence method, it is concluded that the above N-1 behaviour is not caused by shear-induced homogenization, but is probably caused by the shear-induced alignment of the microdomain structure.