To provide a skin slip-off preventing structure for the monolithic foam molding of a skin for certainly holding the skin at the time of mold clamping and capable of reducing the amount of a material used in the skin while keeping predetermined quality to contribute to cost reduction.

In the skin slip-off preventing structure for the monolithic foam molding of the skin for injecting a foamable raw material on the skin 1 set to a cavity mold 2a to perform the monolithic foam molding of the skin by closing a press mold 2b, the skin 1 has a product part 11 and a skirt part 12 and a plurality of wavy uneven parts 121 running in the direction almost vertical to the mold closing insertion direction of the press mold 2b are formed to the skirt part 12 and a plurality of wavy uneven parts 211 are formed to the mold surface 21a of the cavity mold 2a corresponding to the wavy uneven parts 121 so as to fit the wavy uneven parts 121 and the wavy uneven parts 211 when the skin 1 is set to the cavity mold 2a.