The invention relates to a horizontal displacement amplification device. The horizontal displacement amplification device comprises a box girder section, a gear set, a gear shaft, a hinged shaft support, a high-strength bolt, an upper rack plate, a lower rack plate and a shearing type damper. The structure horizontal displacement is amplified by multiple times through the gear set to be transmitted to the damper, the shearing type damper can bring a very good energy dissipation damping effect into play, and the horizontal displacement amplification device is suitable for the anti-seismic design of structures, such as a shearing wall and a frame cylinder, with small structural interlayer displacement. For the purpose of increasing the application range, the shearing type damper can be designed and used for a small earthquake or wind vibration, and the box girder section is designed into two-section energy dissipation and used for resisting an earthquake which rarely occurs.