This paper discusses about device characterization for mmW transceiver design. Especially, the de-embedding error is evaluated with a 60 GHz 4-stage amplifier and measured data of transmission line. According to a comparison of characteristic impedances of transmission line which are derived by Thru-only and L-2L de-embedding methods, there are about 5.9% error at 60 GHz in Thru-only one and less than 1.7 % error in L-2L one. The error is also evaluated with the 4-stage amplifier, and it results in 1.5 dB gain error and 2.6 GHz frequency shift.