Provided is a folding packaging cooler box convertible from a box mode to an unfolding mode or vice versa, comprising: a box portion having a bottom portion, sidewall portions and joint portions configured to connect with one another and to form a single plane in the unfolding mode; and a cooling reinforcing portion configured to be inserted to the inside of the box and to form a hexahedron shape together with said box portion when said box portion is converted into the box mode, wherein said cooling reinforcing portion comprises a reinforcing bottom portion configured to form a lower surface and to face the bottom portion of the said box portion upon conversion into the box mode; reinforcing sidewall portions configured to connect with the said reinforcing bottom portion and to face the sidewall portions of said box portion; and reinforcing joint portions configured to join said reinforcing sidewall portions, to be folded to face itself and to be in close contact with the reinforcing sidewall portions, upon conversion into the box mode, and wherein said reinforcing bottom portion, said reinforcing sidewall portions and reinforcing joint portions form a single plane in the unfolding mode.