Focusing and selecting the HBr-N2O cluster beam was performed by using a 2 m long electrostatic hexapole field. The observed focusing curve shows a clear evidence that the linear type HBr-N2O isomer which has symmetry of symmetric top was preferentially detected in the cluster beam formed under the experimental condition used here, even though our previous ab initio calculations predict that the bent type isomer is theoretically possible. The best fit simulation for the experimental focusing curve was achieved only if we assume vibrational excitation in the van der Waals mode of the linear type HBr-N2O. The permanent dipole moment is determined to be 0.50+/-0.05 D.