An interference analysis device for analyzing interference between wires provided on a circuit board and including a coupled line, comprising: an input unit that inputs design data representing an arrangement of the wires on the circuit board; a selection unit that selects, as an analysis region, at least a part of the circuit board represented by the design data; a division unit that divides the wires in the analysis region into segments to be units for calculating a circuit matrix; a calculation unit that calculates a circuit matrix with respect to a coupled line constituted by a plurality of segments adjacent to each other among the segments divided by the division unit; an analysis unit that obtains a degree of electromagnetic interference between the wires in the analysis region based on the circuit matrix, characterized in that the calculation unit calculates the circuit matrix of the coupled line, using an asymmetry parameter ASP representing asymmetry of the coupled line and RLGC parameters containing a resistance, an inductance, a parallel conductance, and a capacitance of a transmission line in the coupled line, wherein the asymmetry parameter interpolates asymmetry of the asymmetric coupled line to enable the asymmetric coupled line to be dealt with as a symmetric coupled line by rotating the circuit matrix mathematically by an angle Θ - π/4 wherein tan Θ = ASP so that an odd mode and an even mode have a symmetric relationship of 1:1 in the asymmetric coupled line, wherein the asymmetry parameter is calculated by the following expression in a coupled line constituted by a first line and a second line: ASP = impedance in a case where the first line is present alone / impedance in a case where the second line is present alone 1 / 2. an input unit that inputs design data representing an arrangement of the wires on the circuit board; a selection unit that selects, as an analysis region, at least a part of the circuit board represented by the design data; a division unit that divides the wires in the analysis region into segments to be units for calculating a circuit matrix; a calculation unit that calculates a circuit matrix with respect to a coupled line constituted by a plurality of segments adjacent to each other among the segments divided by the division unit; an analysis unit that obtains a degree of electromagnetic interference between the wires in the analysis region based on the circuit matrix, characterized in that the calculation unit calculates the circuit matrix of the coupled line, using an asymmetry parameter ASP representing asymmetry of the coupled line and RLGC parameters containing a resistance, an inductance, a parallel conductance, and a capacitance of a transmission line in the coupled line, wherein the asymmetry parameter interpolates asymmetry of the asymmetric coupled line to enable the asymmetric coupled line to be dealt with as a symmetric coupled line by rotating the circuit matrix mathematically by an angle Θ - π/4 wherein tan Θ = ASP so that an odd mode and an even mode have a symmetric relationship of 1:1 in the asymmetric coupled line, wherein the asymmetry parameter is calculated by the following expression in a coupled line constituted by a first line and a second line: ASP = impedance in a case where the first line is present alone / impedance in a case where the second line is present alone 1 / 2.