An electrospinning technique was first developed to fabricate Bi2WO6 nanofibrous mat with excellent photoactivity under visible light. The nanofibers are made of single-crystalline Bi2WO6 nanoparticles about 100 nm in size. The diameters of the nanofibers can be controlled by simply tuning the weight ratio of Bi2WO6 to poly(vinyl pyrrolidone) (PVP) (R). With the value of R increasing, the average diameter of the nanofibers was decreased. In addition to the favorable recycling characteristics, the mat with R = 2 exhibits higher photocatalytic activity in the decomposition of acetaldehyde (CH3CHO) and aqueous ammonia than that of the sample prepared by solid-state reaction (SSR) and the nanoparticles. Such an advantageous electrospinning route, which not only brings effective improvement in the photocatalytic activity of catalysts but also provides a solution to the separation problem for conventional catalysts that are small in size, is worth considering for the preparation of other photocatalysts.