A head-mounted display including a body, a bearing base, a separation plate, a knob, a guiding element, a first gear, a second gear and a head belt set is provided. The separation plate is fixed inside the bearing base. The knob is pivoted to the bearing base and located outside the bearing base. The guiding element is pivoted to the bearing base and located inside the bearing base, and is configured to be driven by the knob to rotate. The guiding element includes a shaft portion passing through the bearing base and the separation plate. The first gear and the second gear are sleeved on the shaft portion, and are separated from each other by the separation plate. The head belt set connects the body and the bearing base. The head belt set includes an auxiliary head belt, a first side head belt and a second side head belt.