For determination as to whether there is a possibility that temperature control satisfying conditions according to an upper limit LH_i and a lower limit LL_i of the annealing control temperatures of annealing object steel sections i will be realized under restrictions on limit values U and D of the control temperature increase and decrease rates, computation is performed without using dynamic programming requiring an enormous amount of data on a continuous annealing line of a steelwork. Annealing object steel sections in an annealing object steel band 12 to be computed are assigned numbers 1, 2, . . . , n in order from the first time division in the direction of movement. T_i is a time required to pass the annealing object steel section i through a predetermined point at which the steel section undergoes temperature control. LH_1nullLL_1nullb is given. X_inullnullIL_inullD*T_i, IH_inullU*T_inull is computed. When X_ L_i1 f, Y_inullX_i L_i. When X_i L_inullf, Y_inullX_i. Ynulli is computed from inull1 to inulln in ascending order.