A memory device includes m memory cell blocks, m×(k+1) word lines, n bit lines, and a word line driver circuit (m, k, and n are each an integer greater than or equal to 1). The memory cell block includes memory cells of (k+1) rows×n columns, and each of the memory cells is electrically connected to a word line and a bit line. The word line driver circuit has a function of outputting signals to m×k word lines that are selected from m×(k+1) word lines by using a switch transistor, and selection information is written to a gate of the switch transistor by using a transistor having a low off-state current. The memory cells of k rows×n columns included in the memory cell block are normal memory cells, and each of the memory cell blocks includes redundant memory cells of one row×n columns.