We image the spatial extent of a cool galactic outflow with fine-structure Fe ii* emission and resonant Mg ii emission in a gravitationally lensed star-forming galaxy at z= 1.70347. The Fe ii* and Mg ii (continuum-subtracted) emissions span out to radial distances of∼ 14.33 and 26.5 kpc, respectively, with maximum spatial extents of∼ 21 kpc for Fe ii* emission and∼ 30 kpc for Mg ii emission. Mg ii emission is patchy and covers a total area of∼ 184 kpc 2, constraining the minimum area covered by the outflowing gas to be∼ 13% of the total area. Mg ii emission is asymmetric and shows∼ 21% more extended emission along the decl. direction. We constrain the covering fractions of the Fe ii* and Mg ii emission as a function of radial distance and characterize them with a power-law model. The Mg ii 2803 emission line shows two kinematically distinct emission components and may correspond to two distinct shells of outflowing gas with a velocity separation of Δv∼ 400 km s− 1. By using multiple images with different magnifications of the galaxy in the image plane, we trace the Fe ii* and Mg ii emissions around three individual star-forming regions. In all cases, both the Fe ii* and Mg ii emissions are more spatially extended compared to the star-forming regions traced by the [O ii] emission. These findings provide robust constraints on the spatial extent of the outflowing gas and, combined with outflow velocity and column density measurements, will give stringent constraints on mass-outflow rates of the galaxy.