A gas flow adjusting device (1) is provided, which includes a tube body (11), a first horizontal shaft (12A), a second horizontal shaft (12B), two leaf structures (13), a torsional spring (14) and two linkage assemblies (15). The first and second horizontal shafts are disposed in an accommodating space of the tube body and spaced apart from each other along an axial direction of the tube body. The leaf structures are pivoted on the first horizontal shaft and have a swinging direction identical to the axial direction. The torsional spring is sleeved around the second horizontal shaft and provides a resilient force along the axial direction. The linkage assemblies are connected to the leaf structures respectively, and each of the linkage assemblies is connected to the second horizontal shaft and the torsional spring. Therefore, when the leaf structures swing to different angles, the twisting amounts of the torsional spring are minimally varied.
