We present observational results of galactic outflows from star-forming galaxies at z~0--2 based on optical spectra with absorption lines. The spectra of galaxies at z~0, 1, and 2 are taken from the large-survey data sets of SDSS DR7, DEEP2 DR4, and Erb et al. 2006, respectively. We carefully construct large and homogeneous samples with similar stellar mass distributions ranging from 10^9 to 10^11.5 solar mass. We stack the galaxy spectra and perform the multi-component fitting of model absorption lines to the stacked spectra. We identify, for the first time, that the average outflow velocity monotonically increases by 0.1--0.4 dex from z~0 to 2 at the >~ 2 sigma levels at a given star formation rate. Moreover, we find that the mass loading factor increases at a given halo circular velocity, albeit with a potential systematics caused by model parameter choices.