A shell for a bicycle saddle, comprising: a body provided with a top surface, a bottom surface, a groove through the top surface and the bottom surface, a narrow anterior portion for fitting between a cyclist's crotch, a wide posterior portion for supporting the cyclist's buttocks, and two sockets for insertion of a supporting frame; wherein, the narrow anterior portion has a front edge; the wide posterior portion has a rear edge and two lateral edges extending from two ends of the rear edge substantially toward the front edge; the body is defined with an imaginary longitudinal axis which substantially passes through the front edge, the rear edge and the groove and divides the wide posterior portion into a left region and a right region; the groove is provided at the wide posterior portion with a longitudinal section having a front end and a rear end and extending from the front end substantially along the imaginary longitudinal axis toward the rear edge to the rear end, and a transverse section extending from the rear end of the longitudinal section to the left region and the right region of the wide posterior portion so that the wide posterior portion has two elastic wings adjacent to the groove; whereby the two sockets are located at the left region and the right region of the wide posterior portion respectively; the shell being characterized in that each of the sockets has a connecting sheet connected with the rear edge and one of the lateral edges of the wide posterior portion and extending to a position under the bottom surface, and an insertion block connected with the connecting sheet; a space is provided between each of the sockets and the bottom surface; and in that the transverse section of the groove has a convex edge facing the rear end of the longitudinal section so that the wide posterior portion has a convex sheet protruding toward the rear end of the longitudinal section. a body provided with a top surface, a bottom surface, a groove through the top surface and the bottom surface, a narrow anterior portion for fitting between a cyclist's crotch, a wide posterior portion for supporting the cyclist's buttocks, and two sockets for insertion of a supporting frame; wherein, the narrow anterior portion has a front edge; the wide posterior portion has a rear edge and two lateral edges extending from two ends of the rear edge substantially toward the front edge; the body is defined with an imaginary longitudinal axis which substantially passes through the front edge, the rear edge and the groove and divides the wide posterior portion into a left region and a right region; the groove is provided at the wide posterior portion with a longitudinal section having a front end and a rear end and extending from the front end substantially along the imaginary longitudinal axis toward the rear edge to the rear end, and a transverse section extending from the rear end of the longitudinal section to the left region and the right region of the wide posterior portion so that the wide posterior portion has two elastic wings adjacent to the groove; whereby the two sockets are located at the left region and the right region of the wide posterior portion respectively; the shell being characterized in that each of the sockets has a connecting sheet connected with the rear edge and one of the lateral edges of the wide posterior portion and extending to a position under the bottom surface, and an insertion block connected with the connecting sheet; a space is provided between each of the sockets and the bottom surface; and in that the transverse section of the groove has a convex edge facing the rear end of the longitudinal section so that the wide posterior portion has a convex sheet protruding toward the rear end of the longitudinal section.