A spectroscopic detector includes a lamp house, a sample cell, an optical sensor, a heater, a cooling fan, a temperature sensor, and a control device. The heater heats the lamp house while being directly or indirectly in contact with the lamp house containing a light source. The cooling fan is for cooling the lamp house. The temperature sensor is for detecting a temperature of the lamp house. The control device is configured to control operations of the light source, the heater, and the cooling fan. The control device includes a temperature control part configured to maintain a temperature of the lamp house while the light source is lit at a set temperature by controlling at least output of the heater based on a detection signal of the temperature sensor.