documentclass{article}
usepackage{booktabs}
begin{document}
  begin{table*}centering
    begin{tabular}{@{}lccccccc@{}}toprule
      & multicolumn{3}{c}{A} & phantom{abc}& multicolumn{3}{c}{B}\ cmidrule{2-4} cmidrule{6-8}
      & 1 & 2 & 3 && 1 & 2 & 3\
      midrule
      C     &       0.60  &       0.951 &       0.245         & &       1.151         &       1.563         &       0.586         \
                  &     (0.262)         &     (0.364)         &     (0.310)         & &     (0.620)         &     (0.905)         &     (0.696)         \
      midrule
      (N)       &      919629         &      468093         &      451536         & &      186271         &       94771         &       91500         \

      bottomrule
    end{tabular}
  end{table*}
end{document}