Dynamical properties of bulk poly(propylene sulfide) (PPS) were investigated for a range of molar masses between 600 and 50 000 g/mol. The primary and secondary relaxation (alpha-relaxation and beta-relaxation) were studied using dielectric spectroscopy. The local segmental relaxation (alpha-relaxation) and the chain backbone conformational relaxation were studied using dynamic mechanical measurements. The dynamical properties of PPS are compared to those of poly(propylene oxide) (PPO) and are shown to be very similar. However, the glass transition temperature of PPS decreases strongly for low molar masses, while for PPO it is almost independent of the molar mass down to 400 g/mol.