The transactinide nuclei, ²⁶¹Rf and ²⁶²Db, have been produced in the ²⁴⁸Cm (¹⁸O, 5n) reaction at beam energies of 91, 94, and 99 MeV, and in the ²⁴⁸Cm (¹⁹F, 5n) reaction at 106 MeV, respectively. The production cross sections are evaluated from the mother-daughter correlations of α energies between ²⁶¹Rf and ²⁵⁷No, and ²⁶²Db and ²⁵⁸Lr. The maximum cross section of the ²⁴⁸Cm (¹⁸O, 5n) reaction is measured to be 13±3 nb at around 94 MeV, while the production cross section of ²⁶²Db in ²⁴⁸Cm (¹⁹F, 5n) is 1.3±0.4 nb at 106 MeV.