In a rotary shaft seal configured such that first and second seal elements (1) and (2) each having a fundamental thickness (T) and each curved through a curved wall portions (5) of a corresponding one of the first and second seal elements (1) and (2) to have a generally J-shaped cross section are arranged so as to be curved in opposite directions along a shaft center (L), a wide circumferential groove (7) is formed in each of opposed surfaces (6) of the respective curved wall portions (5) of the first and second seal elements (1) and (2). Under use conditions (where the seal is inserted), extreme end portions (8) of the first and second seal elements (1) and (2) are in contact with an outer circumferential surface (9a) of a rotary shaft (9) with a peak contact pressure such that a contact width (E) is equal to or less than twice the fundamental thickness (T).