We performed the inelastic neutron scattering experiment on a powder sample of YbSb in order to clarify the nature of the unusual non-magnetic phase transition at 5 K. The two broad magnetic peaks at {\sim }13 meV and {\sim }18 meV were observed, as reported by the previous inelastic neutron experiment. The clear difference of these magnetic excitation spectra between the paramagnetic phase and the ordered phase may indicate the change of the 4f electronic states due to the phase transition at 5 K. Furthermore a new magnetic excitation below {\sim }3 meV, which is common feature in Yb-monopnictudes, was found.

PACS numbers: 71.27.+a, 75.30.Mb, 71.70.Ch, 78.70.Nx