Tensile creep tests were carried out. for the [011]-oriented Ni-20mass%Cr single crystals at 1173 K in the stresses between 14.7 and 68.6 MPa. The creep curve basically shows a similar shape in every stress; the creep rate scarcely decreases at the early stage of transient creep and then decreases to a minimum creep rate, followed by an accelerating creep. Rupture elongation exceeds 80 % in the higher stresses above 29.4 MPa, while it is around 10 % in the lower stresses. The stress exponent of the minimum creep rate, n, is five in the whole stress region. A heterogeneous formation of substructures in the lower stresses leads to the premature onset of accelerating creep, which reduces the rupture strain and prevents the expansion of transient creep.