  We numerically check that the surface tension of membranes is independent of
the shape of surface boundary. The surface tension is calculated by means of
the Monte Carlo simulation technique on two types of cylinders made of rubans
of size $L_1$ and $L_2$, where the rubans are the same for the projected area
and different in the ratio $L_1/L_2$. The difference of the surface tension
disappears in the thermodynamic limit in both models of Helfrich-Polyakov and
Landau-Ginzburg.
