The utility model discloses an automatic rocking chassis for a baby's bed and a pram, which is a slider-crank mechanism. A crank comprises a speed governor (1), a motor (2), a driving disc (3), and a supporting base (13); a connecting rod (4) is a connecting rod; a sliding block comprises a connecting shaft (5), a cross rod (6), a sliding rod (7), a sliding rod (10), an adjustable rack (11), and a pin (12); a frame comprises a support (8), a support (9), a support (14), and a support (15); a rotation pair comprises the crank and the connecting rod which are connected through a hinge; the sliding block and the frame form clearance fit, and a motion pair is formed. When the crank rotates, the sliding block and a baby's bed or a pram placed on the sliding block are driven through the connecting rod to conduct the reciprocating circle arc movement with a frequency which is coordinate with baby's heart rate along a circular arc groove on the frame.