Spatiotemporal instability of ultrashort pulse beam propagating through cubic nonlinear dispersive media is studied by using an extended nonlinear Schrdinger equation (NLSE). Spatiotemporal focusing, self-steepening and Raman delayed response are identified. The linear stability theory are used to study the growth of small noise from the background of intense laser. It is found that Raman delayed response makes spatiotemporal instability occur in a wider spectrum region, even in an anomalous dispersion region of self-defoucsing media. Based on that, some characteristics about spatiotemperal instability have been studied.