To provide a device to stack and unstack a cart by a lifting frame inside a machine frame capable of applying to several types of carts with different frame widths, and checking stacking condition in the machine frame.

A pair of open/close arms 16 which are moved freely in the horizontal plane by actuation of a clamp cylinder unit 17 is provided to a pair of left and right retaining plates 15 of the lifting frame 3 capable of going up and down in the machine frame 2, and it gets in from a cart frame 6 when the open/close arm 6 is thrust inside. While the open/close arm 16 is thrust inside, the lifting frame 3 is moved up to lift the cart 50 at a specified height, another cart 5 is delivered below, and then the cart 5 lifted above the delivered cart 5 is lowered down to stack on it. Detectors 22a and 22b to detect stacking condition are provided to the machine frame 2.