PURPOSE: To execute balanced line selection corresponding to capacity by checking line using state information obtained by considering line speeds of individual lines at the time of forming paths in plural lines.

CONSTITUTION: Line status information storing mechanisms 3-0∼3-n store the line using status information of individual lines, e.g. load ratios indicating the circuit using status of respective lines, and a line selecting mechanism 2 checks the load ratios and selects any one of the lines. Namely, the mechanism 2 calculates an equality Si(t)=Di×(Lmax/Li)+Si(t-1) for all the lines, selects the line corresponding to the minimum value of the total data volume Si(t) and informs the selected line to a path forming mechanism 1. In the equality, Di is the necessary data volume of a path practically requested to be formed, Lmax is the maximum value of line speeds L1∼Ln, Li is the line speed of the line selected to form a path, and Si(t-1) is the total data volume in the #1 line.