A method for measuring electric circuit parameters of a 2-terminal circuit having first and second terminals, includes steps of: terminating one of the first and second terminals with a terminal impedance Z1, to measure reflection characteristics α1 for the other terminal; terminating one of the first and second terminals with a terminal impedance Z2 different from the terminal impedance Z1, to measure reflection characteristics α2 for the other terminal; terminating one of the first and second terminals with a terminal impedance Z3 different from the terminal impedances Z1 and Z2, to measure reflection characteristics α3 for the other terminal; and calculating electric circuit parameters of the 2-terminal circuit based on the resultant reflection characteristics α1, α2 and α3, whereby measuring electric circuit parameters, such as S-parameters, Z-parameters or the like, even of a DUT having a weak ground, in a simple way with high accuracy and low cost.