Abstract: Disclosed are a method and apparatus for analyzing impedance of a lithium-ion battery. The method according to embodiments includes a transmission line model (TLM) equivalent circuit fitting operation of analyzing measured impedance data and fitting the analyzed impedance data to a TLM equivalent circuit. The TLM equivalent circuit fitting operation includes deriving, through a complex nonlinear least square (CNLS) method, a value at which a difference between an analytical function of the TLM equivalent circuit and the measurement data is minimized. The method according to embodiments may further include a data verification operation of verifying the measured impedance data using a Kramers-Kronig relation.