We report the results of photometric observations of a number of magnetic white dwarfs in order to search for photometric variability in these stars. These V-band observations revealed significant variability in the classical highly magnetized white dwarf GRW+70au broken vertical bar 8247 with a likely period from several days to several dozen days and a half-amplitude of about 0(.) (m) 04. Our observations also revealed the variability of the well-known white dwarf GD229. The half amplitude of its photometric variability is equal to about 0(.) (m) 005, and the likely period of this degenerate star lies in the 10-20 day interval. This variability is most likely due to the rotation of the stars considered.We also discuss the peculiarities of the photometric variability in a number of other white dwarfs. We present the updated "magnetic field-rotation period" diagram for the white dwarfs.