  A method to define the complex structure and separate the conformal mode is
proposed for a surface constructed by two-dimensional dynamical triangulation.
Applications are made for surfaces coupled to matter fields such as $n$ scalar
fields ($n=0,1$ and $4$) and $m$ Ising spins ($m=1$ and $3$). We observe a
well-defined complex structure for cases when the matter central charges are
less than and equal to one, while it becomes unstable beyond $c=1$. This can be
regarded as the transition expected in analytic theories.
