Silicon carbide (SiC) containing He atoms expands by annealing above ∼ 1300°C, owing to the formation and growth of He bubbles. An external compressive stress applied during annealing retards expansion in the stress direction, while promoting it in the lateral directions. It is proposed that He atoms in the bubbles on grain boundaries perpendicular to the compression axis are transported to the bubbles on boundaries parallel to the stress axis. The transport of He accompanies changes in the volumes of the bubbles to maintain equal pressure in all the bubbles. The volume changes of the bubbles are caused by the flow of SiC‐constituting atoms from or to the boundaries where the volume‐changing bubbles exist. This process results in a jacking action which alters the thickness of boundary atom layers. It produces macroscopic strains. The plausibility of the proposed process is examined on the basis of ener