The present invention relates to verification of a transmission margin of various transmission lines transmitting a signal such as a high-speed digital signal and ensures improved verification accuracy. A transmission margin verification apparatus according to the present invention is configured with a measurement unit (e.g., LSI tester 4, network analyzer 6, pulse generator 8, oscilloscope 10) operable to measure a transmission loss and a leading edge waveform of pseudo transmission lines (e.g., transmission lines 56, 62, 66) corresponding to a target device 44 to be verified, and a calculation unit (tester controller 12) operable to reference the transmission line loss and the leading edge waveform measured by the measurement unit, calculate a transmission waveform of the target device, and associate the transmission waveform with a mask of the target device to calculate a transmission margin of the target device.