The invention relates to an accumulation device (4) comprising a first linear conveyor belt (5) and a second linear conveyor belt (6), a third conveyor belt (7) forming a semi-circle and configured for transferring items from the first to the second conveyor belt and translation means (10, 11) of the third belt relative to the first and second belt. The accumulation device comprises two ramp systems (23, 24) attached respectively to the two ends (7a, 7b) of the third belt. The first ramp system (23) deforms the first belt to constitute a first slope ensuring that items rise from the first belt to the third belt. The second ramp system (24) deforms the second belt to constitute a second slope ensuring that items descend from the third belt to the second belt. Displacement of the third conveyor belt at the same time enables displacement of the first and second slopes formed on the first and second belt. The invention also relates to an installation equipped with such an accumulation device.