A mask ROM small in circuit scale and low in consumption power has an n-type select transistor having a drain connected to a corresponding one of bit lines, a source connected to a data line, and a gate having a corresponding one of select signals input thereto. A p-type precharge transistor has a drain connected to a corresponding one of bit lines, a source connected to a power line, and a gate having a corresponding one of the select signals input thereto. Because the bit line is precharged by using a precharge transistor opposite in conductivity type to the select transistors, it is satisfactory to provide one precharge transistor for one bit line, greatly reducing the circuit scale.