We have investigated the molecular dynamics in the chiral smectic phases of an antiferroelectric liquid crystal, (S)-MHPOBC, by means of solid-state¹³C NMR spectroscopy with CP/MAS and MASGHD techniques. In the CP/MAS spectra on heating, the half-width of an aromatic peak increases with increasing temperature in crystalline phase until it attains a maximum at about 75℃, and decrease in smectic phases. Assuming that the observed line broadening of MHPOBC occurs under the condition of ω₁・τ〜1, where ω₁ is a contact time and τ is a correlation time, the crrelation time (τ) of the molecular motion for the core part is estimated to be about 10^-6s.