Factors influencing the secondary ion yield and depth resolution in the SIMS depth profiling of carbon in the tantalum thin films have been investigated. The highest ion yield of C has been achieved with 193TaC- by using Cs+ primary ion beam. However some changes in surface topography during Cs+ ion sputtering were observed. We found that the extent of the changes differed depending on implanted C+ doses and that the depth resolution became lower as the quantity of dosed C increased. These phenomena are supposed to be due to that Ta crystals became amorphous and carbonized.