A method of estimating the current distribution on a microstrip transmission line of a multilayer printed circuit board (PCB) by measuring the near-field distribution is proposed. The microstrip transmission line on the PCB is divided into electrically small segments. An electric field integral equation (EFIE) is established to relate the near field to the current on these segments. The current is estimated by measuring the near field, evaluating the mutual impedance between the current segments, and solving the EFIE. The measurement parameters for near-field measurement are optimized by numerical analysis. Experimental results are presented and compared with the numerical results, confirming the validity of this method.