A high-performance gasket (1) capable of coping with a reduction in size and developing a sealing property without producing a squeeze-out at the time of attachment and using a material having a hardness range of 30 to 80 degrees (JIS durometer type A), wherein the requirement of W1/W0 =3 is satisfied where the length of the non-bonded portion of the base part (1a) around the cross-section thereof excluding the bonded portion is (L), and the compressibility of the gasket when compressed is 13.5% or higher.