A fixing device adapted to be mounted on a wall for connection with an object holder, said fixing device including: a fixing member adapted to be mounted on the wall; a hollow shell body having first and second end surfaces (211, 222), and being formed with a through groove that has a first groove portion extending through said first end surface in a first direction, and a second groove portion extending through said second end surface in a second direction which is substantially perpendicular to the first direction; a first connecting member securely connected to said fixing member, and having a linking portion that extends in the first direction, and that is inserted into said first groove portion of said through groove; and a second connecting member adapted to be connected to the object holder, and having a connecting portion that extends in the second direction, that is inserted into said second groove portion of said through groove, and that is securely connected to said linking portion of said first connecting member; characterized in that: the hollow shell body is made of metal, and the first and second connecting members (3, 4) are made of a plastic material, and in that one of said linking portion of said first connecting member and said connecting portion of said second connecting member has two engaging grooves (311, 412); and the other one of said linking portion of said first connecting member and said connecting portion of said second connecting member has two hooks (411, 313) engaging directly and respectively said engaging grooves (311, 412). a fixing member adapted to be mounted on the wall; a hollow shell body having first and second end surfaces (211, 222), and being formed with a through groove that has a first groove portion extending through said first end surface in a first direction, and a second groove portion extending through said second end surface in a second direction which is substantially perpendicular to the first direction; a first connecting member securely connected to said fixing member, and having a linking portion that extends in the first direction, and that is inserted into said first groove portion of said through groove; and a second connecting member adapted to be connected to the object holder, and having a connecting portion that extends in the second direction, that is inserted into said second groove portion of said through groove, and that is securely connected to said linking portion of said first connecting member; characterized in that: the hollow shell body is made of metal, and the first and second connecting members (3, 4) are made of a plastic material, and in that one of said linking portion of said first connecting member and said connecting portion of said second connecting member has two engaging grooves (311, 412); and the other one of said linking portion of said first connecting member and said connecting portion of said second connecting member has two hooks (411, 313) engaging directly and respectively said engaging grooves (311, 412). the hollow shell body is made of metal, and the first and second connecting members (3, 4) are made of a plastic material, and in that one of said linking portion of said first connecting member and said connecting portion of said second connecting member has two engaging grooves (311, 412); and the other one of said linking portion of said first connecting member and said connecting portion of said second connecting member has two hooks (411, 313) engaging directly and respectively said engaging grooves (311, 412).