We demonstrated the mapping of the spatial oscillation of electric fields in the transverse plane of a femtosecond Bessel-Gaussian laser beam from the first principle of classical electrodynamics. An attosecond burst of electrons for probing the electric force was placed in the Bessel beam through photoemission with single isolated 276 as extreme ultraviolet pulses. The direction reversal of the electric field in adjacent Bessel rings was directly confirmed by observing the momentum shift of the probe electrons.