  A role of umklapp scattering has been examined for two-coupled chains with
both forward and backward scatterings by applying renormalization group method
to bosonized Hamiltonian. It has been found that a state with relevant
interchain hopping changes into a state with irrelevant (confined) one when the
magnitude of umklapp scattering becomes larger than that of interchain hopping.
Critical value of umklapp scattering for such a confinement-deconfinement
transition is calculated as the function of interchain hopping and intrachain
interactions. A crossover from one-dimensional regime into that of coupled
chains is also shown with decreasing temperature.
