  Wormhole is defined as the topological structure with the throat connecting
two asymptotically flat spaces. In order to have and maintain the structure of
the wormhole, there needs the geometrical flare-out condition, i.e., the
minimal size at throat. In the case of Morris-Thorne type wormhole, the
condition is given by the huge surface tension compared to the energy density
times the square of the light speed. In this paper, we re-considered the
flare-out condition for the wormhole with the Einstein equation, checked the
finiteness of the pressure, and investigated its physical meaning.
