A head-mounted display device is provided. The head-mounted display device includes: a frame having one surface formed to face a user's face; a wearing part formed to be coupled to at least a part of the frame so as to allow the frame to be fixed to the face; a mounting part formed in a cavity structure so that an external electronic device is capable of being mounted on the other surface of the frame; and one or more fastening parts that fix the external electronic device to the mounting part, wherein the fastening parts has an inclined opening angle.