Huge amount of excavated rock is generated in tunnel construction for roads and railways. The excavated rock contains toxic trace metals and/or metalloids at the same level or slightly higher than background level. Our previous studies showed that in the column leaching test, the amount of arsenic leached from the excavated rock till the arsenic concentration was steadily below 0.01 mg/L was comparable with the amount of the first two arsenic fractions in the sequential extraction. In this study, the leachable arsenic fraction was removed from the excavated rock (mudstone) sample in order to obtain the excavated rock sample which artificially undergoes the leaching process. The column leaching test using the leachable-arsenic-arsenic-fraction-removed sample shows the behavior of arsenic leaching was different depending on the samples. They decreased from 66% to 31% of summed amounts of F1 and F2 arsenic fraction in the sequential extraction, respectively.