Common rail fuel injection apparatus with a flow damper

A flow damper (31) is provided with a clearance (±) to absorb a deformation occurring in proximate to a lower end of the valve body (32). The clearance (±) is located on an entire outer circumference of a lower side of a large diameter portion (51) of a piston (33). By the configuration in this manner, even if a slight deviation in the accuracy or the shape of the seat surface causes a radially inward deformation of a lower portion of the valve body (32) when the valve body (32) is fastened to the common rail body (20) at a large axial force, the clearance (±) absorbs the deformation. Thus, the deformation of the valve body (32) does not affect the piston sliding hole (43). Accordingly, a sliding clearance of the piston (33) does not change, not to spoil a slide motion of the piston (33).