A pin placement determining method includes calculating a waveform deterioration amount of wires from a noise amount of the wires and wiring loss of the wires, the wires being coupled to a connector on a printed board, comparing the calculated waveform deterioration amount of the wires to an evaluation criteria, evaluating the wires in which the waveform deterioration amount exceeds the evaluation criteria, and replacing corresponding pins of the connectors to which the wires that have been evaluated as exceeding the evaluation criteria are coupled with replacement pins of connectors that have a low noise amount.