The invention provides a body-building sit-up device with an angle convenient to adjust. The body-building sit-up device comprises a
knee joint roller, a first fixing frame, an
ankle joint roller, a supporting plate, a second fixing frame, a supporting frame, a central controller and a
timer, wherein the first fixing frame is provided with an angle adjusting
assembly used for adjusting the direction of the
ankle joint roller relative to the
knee joint roller, and the second fixing frame is provided with a supporting plate adjusting
assembly used for adjusting the angle of the supporting plate; the two sides of the supporting plate are symmetrically provided with two monitoring limiting assemblies which are used for monitoring whether the back of a user lies on the supporting plate or not and clamping the upper body of the user when
back lying time reaches a preset value in the central controller; and each monitoring limiting
assembly comprises an elastic sleeve, a connecting rod frame, a first sliding rod, a first elastic piece, a connecting plate, a pressing plate, a second sliding rod, a limiting plate, a second elastic piece, a third elastic piece, a
pressure sensor, a mounting frame and an adjusting mechanism used for opening the elastic sleeve. With the body-building sit-up device, the angle of the legs of the user during exercise can be adjusted, and the user can be supported in an auxiliary mode when the user cannot get up.