String Field Theory of $c\leq 1$ Noncritical Strings

We construct a string field Hamiltonian for a noncritical string theory with the continuum limit of the Ising model or its generalization as the matter theory on the worldsheet. It consists of only three string vertices as in the case for $c=0$. We also discuss a general consistency condition that should be satisfied by this kind of string field Hamiltonian.