In a method for distributing a transaction in a computer system including a plurality of computers each formed by processors, a plurality of estimated loads are calculated for the computers. Then, a plurality of estimated process time expansion ratios are calculated for the computers, in accordance with the estimated loads and the numbers of processors in the computers. Then, a plurality of load indexes one for each of the computers are calculated in accordance with the estimated process time expansion ratios. Finally, the transaction is distributed in accordance with the load indexes.