A damping insulator restrains vibration to be transmitted between a fuel injection valve and a cylinder head. The fuel injection valve is attached to an insertion hole of the cylinder head. The fuel injection valve includes a stepped portion reduced in diameter in a tapered shape such that an outer-peripheral-side tapered surface is formed to face a shoulder provided in an inlet portion of the insertion hole. The damping insulator restrains the vibration by being provided between the stepped portion and the shoulder. The damping insulator includes an annular tolerance ring having a bottom surface facing the shoulder and an inner-peripheral-side tapered surface facing the outer-peripheral-side tapered surface, and a damping resin layer provided on the bottom surface or the inner-peripheral-side tapered surface of the tolerance ring. The damping resin layer contains heat-resistant resin and damping filler configured to convert vibrational energy into thermal energy.