A Monte Carlo (MC) study is performed to evaluate the surface tension of spherical membranes that may be regarded as the models of the lipid layers. We use the canonical surface model defined on the self-avoiding triangulated lattices. The surface tension is calculated by keeping the total surface area A constant during the MC simulations. In the evaluation of , we use A instead of the projected area , which is unknown due to the fluctuation of the spherical surface without boundary. The pressure difference between the inner and the outer sides of the surface is also calculated by maintaining the enclosed volume constant. Using and the Laplace formula, we obtain the tension, which is considered to be equal to the frame tension conjugate to , and check whether or not is consistent with . We find reasonable consistency between and in the region of sufficiently large bending rigidity or sufficiently large A / N. It is also found that becomes constant in the limit of both in the tethered and fluid surfaces.