A three-dimensional memory device includes: a plurality of word line groups including a plurality of word lines; a plurality of bit line groups extending in a vertical direction and including a plurality of bit lines spaced apart from the plurality of word lines; a plurality of memory cells arranged between the plurality of word lines and the plurality of bit lines and including a switching component and a variable resistance memory component; a plurality of global bit line groups connected to the plurality of bit line groups, wherein each of the plurality of global bit line groups includes a plurality of global bit lines electrically connected to a plurality of bit lines included in one bit line group, respectively; and a pad structure including a plurality of connection units and a plurality of pad layers, wherein the plurality of connection units are connected to the plurality of word line groups.