An eddy current sensor that includes: a probe and a computing unit. The probe has an exciting portion and a detecting portion. The exciting portion includes a first excitation coil that is wound around a non-magnetic bobbin so that a center axis direction is oriented in an x-axis direction and a second excitation coil that is wound around the non-magnetic bobbin to intersect with the first excitation coil so that a center axis direction is oriented in a y-axis direction. The detecting portion includes a detection coil that is arranged at the lower one of two intersecting portions of the first excitation coil and the second excitation coil. An eddy current measurement method for determining the thickness of a hardened layer.