A packaging box is disclosed, which is formed by coupling two packaging structures. The packaging structure includes a baseboard, which has a first side, a second side opposite to the first side, a third side for connecting the first and second sides, and a fourth side opposite to the third side for connecting the first and second sides. The packaging structure includes a first sidewall standing on the first side, and a second sidewall standing on the third sidewall. The packaging structure further includes plural first coupling elements and plural second coupling elements. The first coupling elements are disposed on the first and second sidewalls. The second coupling elements corresponding to the first coupling elements are disposed on the second and fourth sides of the baseboard. Two packaging structures are coupled by coupling the first coupling elements to the second coupling elements to obtain the packaging box.