A determining method includes obtaining terminal information indicating a first object terminal that is among terminals included among partial circuits and subject to determination of whether the first object terminal is an open terminal; obtaining for each terminal, connection information and first attribute information indicating an attribute of any one among an input terminal and an output terminal; generating, by a computer, for each terminal, second attribute information indicating an attribute opposite to the attribute indicated by the first attribute information; and determining, by the computer, whether a state of the first object terminal indicated by the terminal information becomes a high-impedance state, by simulating on the basis of the connection information and the second attribute information, a state of each terminal when a value of a terminal among the terminals and indicated as an output terminal by the second attribute information, is set at a first specified value.