The value of the electronic work function (EWF) is one of the fundamental characteristics of a condensed-state substance. In the present work, using the method of contact potential difference (CPD) [1], the change in the EWF observed at polished surfaces of steel ct-45 and alloy cast iron CI15D7 under under their exposure to an amplitude-modulated sinusoidal magnetic field at the frequency of 5.28 МHz [2] has been investigated. It has been established that as regards an austenite iron an applied magnetic pulse processing (MPP) leads to an increase in CPD average values for a sample average in the range from -45 mV -18 mV. The observed increase in the CPD values can be associated with a deforming action of a magnetic field. As a result of MPP, the double-mode histograms of CPD distributions typical for unprocessed samples acquired the form close to that of Gauss. This is indicative of leveling the physicochemical and mechanical properties of cast iron surface resulting from MPP; and it reveals recrystallization of the alloy matrix that proceeds under the action of a pulse magnetic field and is accompanied by an increase in surface hardness, change in morphology of its graphite component as well as in the defect structure of the metallic crystal lattice [2]. The steel ct-45 steel samples were exposured periodically to a pulse magnetic field after three variants of their preliminary processing such as: normalization, quenching from 860°C in water and quenching from 860°C in water with subsequent tempering at 450°C for two hours. It is found out that, unlike the EWF of cast iron, that of the surface steel after its MPP increases (and CPD is decreases, respectively). In this case the CPD values are most substantially changed during MPP of the investigated steel after its quenching and tempering. When a quenched steel sample is subjected to MPP, a significant change in CPD is not observed. The hardness of steel samples after their subjecting to MPP decreases: this effect is more pronounced for a normalized steel state. The hardness decrease is correlated with the decrease in CPD (for normalized samples, the CPD decreases by approximately 30 mV and for tempered samples - by 25 mV). In all the cases MPP resulted in increasing the width of CPD distribution histogram which is indicative of a lower surface homogeneity after processing. One of the probable reasons of the observed CPD changes is that a high-speed microplastic shear deformation proceeds in steels on their MPP, according to the mechanism of twinning and dynamic recrystallization, and, depending on their intensity, it can lead to softening of the alloy [3] and, as a consequence, to the increase in EWF.