A webbing-buckling device of a multi-point seat belt system has a buckle assembly and a tongue assembly. The buckle assembly has a buckle base having a first frame portion and a webbing-locking member slidably inserted through the first frame portion. The tongue assembly is disposed on the buckle assembly and has a tongue base having a second frame portion and a webbing-fixing member slidably inserted through the second frame portion. One of two webbings is inserted between the first frame portion and the webbing-locking member, and the other webbing is inserted between the second frame portion and the webbing-fixing member. Alternatively, the webbing-buckling device has a buckle assembly and two tongue assemblies disposed on the buckle assembly. Each tongue assembly has a tongue base having a second frame portion and a webbing-fixing member inserted through the second frame portion. The webbings are inserted through the tongue assemblies.