To enable any large-sized metallic container to be unnecessary by making an accumulator directly connectable to a pump delivery pipe by providing a pressure variation absorbing member whose volume changed reversible to any change in the internal pressure along the longitudinal direction inside of a tube body in which fluid passes through.

Fluid discharged from the delivery port of a pump flows from the central hole 41A of the first end plate 41 into a flow passage 2 and is discharged from the central hole 42A of the second terminal plate 42. When a pressure in the flow passage 2 rises, the walls on the flow passage sides of air chambers 11a to 11d are pressed to the pipe wall side of a tube body 3 and volume variable parts 1a to 1d are contracted and also the sectional area of the flow passage 2 is enlarged. Thereby, any pressure rise in the flow passage 2 is absorbed. On the other hand, when the pressure in the flow passage 2 descends, because the walls on the flow passage 2 sides of air chambers 11a to 11d are pressed to the central side of the tube body 3 by air pressure sealed in the air chambers 11a to 11d, the volume variable parts 1a to 1d are expanded, resultantly the sectional area of the flow passage 2 is contracted. Accordingly, any pressure drop in the flow passage 2 is absorbed.