The erasing process of stripe domains in eight (111)-oriented garnet bubble films was observed in the presence of an in-plane field. The stripe domain erasing field H*s and the domain erasing field H*k were measured as functions of the azimuthal angle βof the in-plane field. Taking the cubic magnetocrystalline anisotropy into account, a theory of stability of stripe domains subjected to an in-plane field was developed. The main features of the experimental results can be expained qualitatively by this theory. Two theoretical relationships between Hs* and βas well as K1 were found. They are applicable to the cases that the direction of in-plane field is near and not fairly near the 〈110〉 crystallographic axes respectively, and are found to be roughly consistent with the experimental results. In particular, along the 〈110〉axes an analytical expression was obtained:Hk〈110〉* =Hs〈110〉*=Hk1+ K1/2ku-al/h(4pMs/Hk)22/3,which is in good agreement with the experiments.