A design optimization of deburring tools for intersecting holes is presented based on design of experiments and response surface methodology. A deburring tool with hemispherical cutter head mounted on a pivoted shaft was used to deburr intersecting holes easily and quickly. Due to the vibration of the tool during deburring, however, the surface of the deburred edge showed considerable irregularity. Tool dynamics was modeled with ADAMS software with the user-defined subroutines. Based on design of experiments and response surface methodology, the tool design was optimized with respect to tool vibration. Deburring tests with the optimized tool on Al6061-T6 specimens showed significant reduction in surface irregularity represented by an index value change from 1.3 to 0.7 mm.