The long-term X-ray light curve of Centaurus X-3 and its pulse-period history, which were obtained by the All Sky Monitor on board the Ginga satellite from 1987 February to 1991 October, are presented. The pulse-period history shows a monotonic spin-up overlapping a roughly sinusoidal wave structure with a period of 9.23±0.14 yr. The observed light curve shows no correlation with the spin-up history. Since Cen X-3 is considered to be a disk-fed X-ray pulsar, the mass accretion affects the pulse period by means of angular momentum transfer onto the neutron star. In the absence of a correlation between the light curve and pulse period, we conclude that the observed intensity does not represent the mass accretion rate.