The present invention provides a device for generating an abrupt autofocusing beam, comprising a light source module, a metasurface phase modulating element, and a focus lens, wherein the light source module generates an incident light beam, the metasurface modulating element has a first optical receiving surface for receiving the incident light beam, and an optical emitting surface having a plurality of dielectric nano-structures formed thereon for modulating the incident light beam into a diffracted light beam wherein the plurality of nano-structures respectively corresponding to optical-phase mask patterns, and the focus lens is arranged at a side of the optical receiving surface for performing optical Fourier transform of the diffracted light beam obtained from the metasurface phase modulating element.