A dual-shaft synchronous transmission device includes a hinge structure, a driving structure, and a linkage assembly, which are linked with each other. The hinge structure includes a first shaft, a second shaft parallel to the first shaft, and a carrier fixed on the first shaft and having a track slot. The driving structure is sleeved at the first shaft and can be driven by the second shaft. A guiding slot is formed on the outer surface of the driving structure. The linkage assembly includes a linking member sleeved at the guiding slot, a first connecting rod connected to the linking member, a second connecting rod linked to the linking member. The linking member is configured to move along the guiding slot with respect to the driving structure and parallel to the first shaft for driving a column of the second connecting rod in the track slot.