Full-scale experiments in the rippled-bed regime were conducted in an oscillatory water tunnel to study the net sediment transport rate due to oscillatory flows on sloping bottoms (up to 2.6 ∘ ). The tests cover a variety of sinusoidal flows, under which uniform two-dimensional ripples are generated from a coarse sand movable bed. A laser-based bottom profiler was developed to measure ripple geometry and net sediment transport rate. Under the same flow condition, a small bottom slope can slightly change the shape of the equilibrium ripples; for example, ripples become upslope leaning, but the ripple dimensions remain almost unchanged. Ripples are also found to migrate in the downslope direction with uniform speed and permanent shape, which is due to the spatial variation of net bedload transport rate. For a given flow condition, the slope-induced net sediment transport rates are in the downslope direction and increase linearly with the bottom slope. A conceptual model, which is an extension of a sheet flow model (Yuan, Li, & Madsen, 2017, https://doi.org/10.1002/2016JC011996), was also developed. This calibration-free model can reasonably predict the net transport rate, despite that a moderate underestimate (a factor slightly less than 2) is observed. Both our experiments and model suggest that the presence of ripples significantly enhances sediment mixing and leads to a large net suspended-load transport rate, which will not occur under sheet flow conditions. Therefore, net transport rate in the ripple-bed regime can be comparable to that in the sheet flow regime, although the flow condition is much weaker.Plain Language Summary Sediment transport over seabed covered by wave-generated sand ripples (or vortex ripple) is an important coastal process related to many coastal engineering problems (e.g., coastal erosion). Understanding the mechanisms of net (time-averaged) sediment transport is of the primary interest to coastal modelers. The bottom-slope effect, namely, a bottom-parallel gravity force acting on sediment grains, is believed to be a key mechanism, but very few quantitative experimental results or modeling work on this effect are available in the literature. In this study, we conduct a full-scale experiment, in which sinusoidal oscillatory flows over vortex ripples are generated in an inclinable oscillatory water tunnel. Measurements of ripple shape and net transport rate are obtained, and a conceptual model is developed for interpreting experimental results and governing physics. It is found that ripples become slightly upslope leaning on sloping bed, and they migrate in the downslope direction. A net downslope transport rate, which includes a strong suspended-load component, is observed in all tests, and it increases quite linearly with bottom slope. The conceptual model can reasonably reproduce measured net transport rates.