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.