The splitting of levels of the 1s5g and 1s6g configurations of the helium atom in an external magnetic field (0-160 Oe) is obtained by using the fine-structure parameters calculated semiempirically. For each configuration, more than 50 crossings and three anticrossings of Zeeman sublevels are determined. The calculated splittings are compared with those obtained earlier for the lsnp and lsnd configurations of a neutral helium atom.