A method of extracting an equivalent circuit of a T-type transmission circuit measures signals of the first and second terminals to obtain S parameters, converts the S parameters into Z parameters to generate a T-type circuit by using the Z parameters, obtains first to third lead line resistors and first to third lead line inductors in the T-type circuit based on the Z parameters corresponding to constants of the T-type circuit, subtracts the Z parameters corresponding to the T-type circuit from the Z parameters corresponding to all of the equivalent circuit to calculate the Z parameters of a π-type circuit, converts the Z parameters of the π-type circuit into the Y parameters, and calculates first to third coupling capacitances based on the Y parameters.