The invention provides an opening device for bidirectionally and reversely cutting macadam fruit shells, and relates to the field of food processing. The opening device for bidirectionally and reversely cutting the macadam fruit shells comprises a fixing base, a supporting block is fixedly connected to the top of the fixing base, a U-shaped block is fixedly connected to the left side of the supporting block, a transmission device is arranged at the right side of the supporting block and connected with a clamping device, and an adjusting device is connected to the clamping device and provided with a rotating girdling device. According to the opening device for bidirectionally and reversely cutting the macadam fruit shells, a gravity ball can conduct counterclockwise circular movement undercentrifugal force; through the counterclockwise movement of the gravity ball, a trapezoidal block can be driven to deflect counterclockwise, and the trapezoidal block can be in contact with a ball head to drive a transfer rod to move rightwards; through the rightward movement of the transfer rod, a cutting head can be in contact with the outer peels of macadamia fruits, the macadamia fruits are conveniently girdled, and the damage to flesh is reduced.