A model for the mechanism of hydrogen wall pumping in fusion devices has been proposed. In this model the following process is assumed as a trigger for wall pumping: carbon evaporation occurs first under high heat loading of a graphite first wall, and pumping for hydrogen is generated simultaneously due to trapping of energetic hydrogen particles onto the fresh carbon film formed as a result of the carbon evaporation on the wall. The demonstration experiment for the hypothesis has been made in a vacuum coater having physical vapor deposition facilities. It is observed that the wall pumping for hydrogen or deuterium gas occurs in the coater, when carbon vapor is generated with an electron beam evaporator in a hydrogen or deuterium plasma produced with a radio‐frequency discharge, and is deposited on surrounding wall surfaces. As a result of the experiment, the typical pumping speed for the hydrogen or deuterium gas is estimated to be as large as 5×10−2l/s cm2(2×1015molecules/s cm2) at a carbon deposition rate of about 2×1016C/s cm2onto a wall having total surface area of 1000 cm2and in the presence of hydrogen or deuterium plasma having electron density of about 2×109cm−3.