SHAFT SEAL

Provided is a shaft seal configured so that the lifting of a dust lip while the shaft seal is under pressure can be prevented. A shaft seal is mounted in an annular groove (2) formed in an insertion hole (20) penetrating through a female body (B) and is in sliding contact with the outer peripheral surface (1A) of a shaft member (1) inserted into the insertion hole (20) so as to be capable of reciprocating, the annular groove (2) comprising a first side wall surface (13) which is located on the pressure receiving side (R), a second side wall surface (12) which is located on the low pressure side (L), and a groove bottom surface (14). The shaft seal is provided with: a U-shaped seal section (10) located on the pressure receiving side (R) and comprising an inner peripheral lip (3) and an outer peripheral lip (4); and a dust lip (7) protruding to the low pressure side (L). A protrusion is formed on a low pressure-side outer peripheral corner (8) formed between an outer peripheral surface (15) in contact with the groove bottom surface (14) and a support surface (6) facing the second side wall surface (12), and while the shaft seal is under pressure, the protrusion is pressed against the corner (16) between the groove bottom surface (14) and the second side wall surface (12) and is absorbed by the low pressure-side outer peripheral corner (8) due to elastic compressive deformation.