A head-mounted display device includes a display assembly, a rotating assembly, and a fixed assembly. The rotating assembly is connected to the display assembly and includes a motor holder, a motor and a first connecting element. The motor is disposed on the motor holder. The first connecting element has a first accommodating portion and a second accommodating portion, wherein the first connecting element receives a part of the motor and the second connecting element receives a part of the motor holder. The fixed assembly is connected to the rotating assembly. The rotating assembly rotates the display assembly relative to the fixed assembly.