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Digital equipment with various high‐speed, low‐power ICs is vulnerable to electrostatic discharge (ESD) and a method to avoid this problem should be developed. Since ESD often is generated by a human while walking, the ESD generating mechanism must be well understood to prevent ESD. This paper proposes a method to estimate the generated charge by evaluating the potential of the human body while walking. Assuming that the basic human motions consist of the up and down movement of the feet, the potential of the human body and generated charges for every step were measured. As a result, it was found that the potential and charges in the human body caused by steps reach a steady state within 800 ms, the potential is lower than 700 V, and the charges are less than 100 nC. The capacitance of the human body changes according to motion and is around 200 pF. When one foot is raised, the body capacitance is 70 percent of that when both feet are grounded. The body potential is dependent on the kind of foot motion, that is, in continuous walk, the body potential is negative and its absolute value increases continuously. In stepping, the potential vibrates with a constant amplitude. These characteristics can be explained from the charging characteristics for the basic body motions.