We investigate the emergence of local ferroelectricity near SrTiO_3 surface steps under external tensile load using first-principles calculations. Nanoscale strain concentration at the surface step induces the local ferroelectricity in the nanoscale area. We found that the emerged polarization forms a closed-flux vortex pattern, which is characteristic of ferroelectric nano structure. In addition, the size and the strength of polarization vortices enlarge with increasing external load. These results suggeste that we can mechanically realize nanoscale ferroelectrics with the strain concentration fields.