Superconducting properties of SrFe1.85Co0.15As 2 single crystals and their parent material, SrFe2As 2, were investigated by scanning tunneling microscopy and spectroscopy (STM/S). In the parent material, we modeled surface conditions on the in situ cleaved single crystals, based on the observation of 2×1 stripe patterns and √ 2× √ 2 square-lattice patterns in the atomic-resolution topography images and with the help of local density of states measurements. In the STM/S studies on SrFe1.85Co 0.15As2, a robust superconducting gap (2δ large = 17.3 meV) was observed in the conductance spectra measured along a line on the SrFe1.85Co0.15As2 surface. Moreover, an additional small gap-like (2δsmall = 2.9 meV) structure was simultaneously observed. Our observation corroborates the two-gap structures in iron-based superconductors.