Two-dimensional (2D) tin diselenide (SnSe2), a novel layered material with excellent optical and electronic properties, has been extensively investigated in various promising applications, including photodetectors, optical switching, and ultrafast photonics. In this work, SnSe2 nanosheets have been obtained after pretreatment in an alkaloid, exhibiting high optical absorption and electron-enriched properties. Besides, the performances of the prepared SnSe2 in near-infrared (NIR) and mid-infrared (MIR) ultrafast photonics are presented. Notably, by employing the SnSe2-deposited microfiber device as a saturable absorber (SA) exhibiting typical nonlinear optical absorption properties, stable ultrashort pulses and rogue waves are realized in an erbium-doped fiber laser. Furthermore, the SnSe2-deposited SA device is also applied to a thulium-doped fiber laser to achieve stable ultrashort pulses. This study indicates that SnSe2 is expected to be a suitable candidate for ultrafast fiber lasers in the NIR and MIR regions.