A paper sheet accumulating device includes an accumulating part in which paper sheets are accumulated, an impeller that sends the paper sheets to the accumulating part, and a support mechanism that supports the impeller. The support mechanism includes a first rotation shaft that supports the impeller rotatable, a support member provided with the first rotation shaft, a second rotation shaft that supports the support member rotatable in a direction of the support member moving toward and away from the accumulating part, and a biasing member that biases the support member in a direction of the impeller moving toward the paper sheets accumulated in the accumulating part.