NOVELTY - Polymer beads sacrificial template layer and metal oxide precursor are added to a dispersion solution, and the polymer is dissolved to obtain electrospinning solution. The obtained electrospinning solution is electrospun to obtain metal oxide precursor/polymer composite nanofiber layer. The resultant composite nanofiber layer is heat-treated, and sacrificial layer is removed and metal oxide precursor is then oxidized to obtain metal oxide nanofiber having multi-pore structure comprising macropores and micropores.    USE - Manufacture of metal oxide nanofiber used for semiconductor gas sensor for detecting oxidizing gas e.g. nitrogen dioxide and nitric oxide, reducing gas e.g. hydrogen, carbon monoxide, ethanol, hydrogen sulfide and methane, and biomarker gas for disease diagnosis.    ADVANTAGE - The method efficiently provides metal oxide nanofiber having wide pore distribution. The semiconductor gas sensor using metal oxide nanofiber has high sensitivity, and is environmentally-friendly.    DETAILED DESCRIPTION - Polymer beads sacrificial template layer and metal oxide precursor are added to a dispersion solution, and the polymer is dissolved to obtain electrospinning solution. The obtained electrospinning solution is electrospun to obtain metal oxide precursor/polymer composite nanofiber layer. The resultant composite nanofiber layer is heat-treated, and sacrificial layer is removed and metal oxide precursor is then oxidized to obtain metal oxide nanofiber having multi-pore structure comprising macropores and micropores. Micropores and macropores are generated by polymer beads sacrificial layer templates having different diameter. Pore contraction occurs during the heat treatment according to the difference in glass transition temperature corresponding to the type of the polymer when the polymer beads sacrificial template layer is mixed with different types of polymers. Multiple pore distribution structure is generated according to domain in which the metal oxide precursor is contained in the metal oxide precursor/polymer composite nanofiber or there is much content of the membranous polymers domain in case of having the diameter in which polymer beads sacrificial layer template is same.