Influences of local field-concentration on surface flashover characteristics of spacers in SF6-gas-insulated coaxial electrode systems were investigated. Flashover tests and field calculations were performed for disc-type and post-type spacers with local field-concentration near the outer electrode The results for disc-type spacers show that the influence of local field-concentration on flashover becomes remarkable at the high pressure range. Results of tests and calculations of post-type spacers confirmed that under certain conditions local field-concentrations caused by field singularity near the gas-epoxy-electrode interface reduced flashover voltages, but also that the flashover characteristics of such spacers were able to be improved by some slight changes of conditions near the interface.