To provide a packing box that can have a cushioning structure easily formed.SOLUTION: A packing box 1 comprises a pair of lower inner flaps 13 connected to a pair of first side walls 10A, and a pair of lower outer flaps 14 connected to a pair of second side walls 10B, the lower inner flap 13 includes a cushioning part 17 (cushioning structure 18) which protects a corner part 91 of a packed object 90, and the cushioning part 17 includes a first plane part 21 in a right-angled triangular shape, a second plane part 22 connected to a hypotenuse common to the first plane part 21 through a positive fold line 25 and in a right-angled triangular shape, and a side face part 23 connected to the second plane part 22 through a reverse fold line 26. In a process of layering the second plane part 22 on the...
