Seat adjusting device for exercise bicycle and sitting type exercise bicycle

The seat adjusting device comprises a frame and a seat mechanism which is arranged on the frame in a front-back position adjustable mode, the seat mechanism comprises a sliding assembly, a seat and a positioning assembly, the sliding assembly comprises a main body frame and a sliding block fixedly arranged at the bottom of the main body frame, and the sliding block is arranged on the frame. The seat is installed at the top of the main body frame, the positioning assembly is arranged at the bottom of the main body frame in an up-down rotating mode, a guide rail and a toothed plate are arranged at the top of the frame, a plurality of clamping openings are formed in the toothed plate in the front-back direction, and the sliding block is in sliding fit with the guide rail; the elastic piece is used for providing downward pre-tightening force for the positioning assembly, when the positioning assembly is lifted, limiting fit between the positioning assembly and the clamping opening of the toothed plate is relieved