An apparatus for generating a reference voltage in a semiconductor memory apparatus according includes: a first voltage generating unit configured to generate a voltage proportional to temperature; a second voltage generating unit configured to generate a voltage inversely proportional to temperature; and a reference voltage generating unit including a first adjusting unit connected with the first voltage generating unit and a second adjusting unit connected with the second voltage generating unit, configured to select the first adjusting unit or the second adjusting unit according to a difference between a reference voltage obtained by the first voltage generating unit and the second voltage generating unit and a target voltage, and adjust the reference voltage thereby outputting a constant reference voltage regardless of a variation in temperature.