To provide a strut mount insulator which does not generate abnormal sound when using it.

This strut mount insulator 2 is constituted, by storing a core material 10 to which stopper rubber 20 is adhered in a casing 8, fixing the core material 10 on an upper end of a piston rod 6 and fixing the casing on a car body panel 4. In this case, a cylindrical outer ring 26 to be press fitted on an inner peripheral surface of the casing 8 is adhered on an outer peripheral surface of the stopper rubber 20, a ring first plate 22 and a second plate 24 are respectively adhered on both end surfaces of the stopper rubber 20, and the stopper rubber 20 is compressed preliminarily in the axial direction of the piston rod 6 in the casing 8 via these first and second plates 22, 24.