We demonstrate the spatial mapping of the spin pumping from a magnetic insulator, yttrium iron garnet (YIG), using the inverse spin Hall effect. The inverse spin Hall effect in thin Pt wires placed on a YIG film enables local detection of the spin-current emission from the insulator, revealing spatially nonuniform spin pumping at various microwave excitation frequencies. We found that the spatial variation of the spin pumping is sensitive to the wavelength of the magnons responsible for the spin pumping as well as the thickness of the magnetic insulator. These findings provide an important information for studying spintronic phenomena in metal/insulator bilayers.