Provided are a surface-treated glass cloth capable of enhancing insulation reliability when used to prepare a prepreg, a prepreg and a printed wiring board using the surface-treated glass cloth. The surface-treated glass cloth includes a surface treatment layer on a surface, a glass constituting the glass cloth has a composition containing 52.0 to 60.0 mass % of SiO2, 15.0 to 26.0 mass % of B2O3, 9.0 to 18.0 mass % of Al2O3, 1.0 to 8.0 mass % of MgO, 1.0 to 10.0 mass % of CaO, 0 to 6.0 mass % of SrO, 0 to 6.0 mass % of TiO2, and 0.1 to 3.0 mass % in total of F2 and Cl2, based on the total amount of the glass, the glass cloth has a surface coverage of 75.0 to 100.0% and a thickness of 8 to 95 μm, and the surface treatment layer contains a silane coupling agent having a methacrylic group and contains no surfactant.