An object of the present invention is to provide an accumulator including a flow damper which is capable of performing a control so that a vortex may not be formed in a vortex chamber at the time of a large flow injection without requiring huge labors and fabrication costs. The flow damper is configured of a colliding jet controller (a bevel or a projection) for controlling a colliding jet composed of a jet from a large flow pipe and a jet from a small flow pipe flowing into a vortex chamber at the time of a large flow injection so that the colliding jet may proceed directly to an outlet without forming a vortex in the vortex chamber. The colliding jet controller is provided at a junction of an inner surface of the small flow pipe and an inner surface of the vortex chamber.