A wall hanging fixing device includes a decoration cover which is provided with a hanging member in its inner side. The hanging member is fixed on a supporting seat in the inner side of the decoration cover with screws. The hanging member is provided with a hanging connection groove which is fit with a supporting member. The fixing device is also provided with a movable member that can move towards or away from the hanging connection groove. It is easy and quick to install the wall hanging fixing device. After an expansion bolt is fixed, the hanging member of the fixing device is hung on the expansion bolt without any disassembly, so as to protect the bathroom articles, and the hanging member can be fixed. This design effectively prevents loosening.