This work was discussed on the morphology and crystal structure on electrospun fibrous PB membrane, namely, both highly porous PB film and the fibrous PB nonwoven prepared by the same method of electrospinning process. Both the tip-to-collector distance (TCD) and the surrounding temperature were crucial parameters for determining the resulting morphologies. In terms of shorter TCD (below 10 cm) and lower surrounding temperature (below $40^{circ}C$), highly porous PB film was almost electrospun because such shorter distance and lower temperature were completely not enough to evaporate the used solvents during electrospinning. Fibrous PB nonwoven, however, was obtained at longer TCD and higher temperature ($80^{circ}C$). X-ray diffraction (XRD) and differential scanning calorimeter (DSC) analyses demonstrated that a porous PB film revealed two crystal structures of dominant form III and small amount of form II arising from the melt recrystallization from form III crystals, while fibrous PB nonwoven showed form I due to the aging time over 2 weeks at room temperature after electrospinning. As a result, it was found that PB membrane can exhibits a porous film and fibrous nonwoven with different morphologies and crystalline microstructures depending on TDC and surrounding temperature although they were prepared from the same method of electrospinning.